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Aquaponics--is passive circulation possible? Looking for ideas

Lauren Ritz

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I can get IBC totes relatively easily, link them together, cut the tops off and invert them for plant rafts.

As with everything else I do, if I'm going to do aquaponics I want it to be input free, which means no pumps or electric filters of any kind.

I'm just not sure if my ideas for circulating water without the use of pumps would actually work.

First, assume two tanks (if it works for 2 it can easily work for more). Between the two tanks are four pipes, two going from the middle to the top, two going from the bottom to the middle on opposite sides. Probably have some kind of flange or cup at the top end. As surface water cools it falls into the top pipes, draining water into the other tank. If I'm seeing this correctly it should create a constant (if small) circulation between the two tanks. As cooler water warms, a similar setup forces warmer water into the other tank.

The other alternative is two pipes, each going through the IBC totes at the bottom (one in each) and terminating at the top of the opposite tank. Black at the bottom, they will absorb sunlight. Heated water will rise through the pipe, creating a constant circulation between the two tanks.

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Dylan Urbanovich

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This is an interesting idea, one that I have spent a little time pondering. The problem you will face is equilibrium. The surface water falling as it cools would work only if the water below is warmer than the surface water. You would either need to find a way to warm the bottom water column or find a way to cool the upper water column by quite a bit to make it more dense than the layers beneath. This would be easier than heating the upper layer, but at some point the whole mass will reach equilibrium and be the same temperature throughout, shutting down your circulation system.

The black pipe would need to be outside the tank in order to heat up enough to warm the water more than it's surrounding mass of water, alternately what if you painted the bottom outside surface of the IBC black? This might heat up the water directly inside the tank on that edge to cause some circulation.

I don't see a way to achieve circulation with 0 inputs, but I could see this system working with passive inputs like geothermal or solar heat harvesting. But then again I am only an armchair physicist.

I would be interested in twinning this system with a trombe wall or environmental earth battery to provide the passive heating.

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Lauren Ritz

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Yes, passive inputs are fine. I just don't want to (ever!) use electricity for these systems. The 2nd option would be passive solar in essence, collecting heat in the black pipes. This might work better during the winter than the summer, since the front side would be sun facing (inside the greenhouse) and the bottom would have the thermal buffer of the soil.

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Dylan Urbanovich

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Ok, what if you were to bury a loop of pipe 8 feet down that was connected to the bottom and top of the tote, theoretically that water would be geothermal heated enough to circulate. You could also sink the tote into the ground a couple feet to better insulate more surface area of the mass.

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Nathanael Szobody

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You could have a windmill circulate your water.

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Lauren Ritz

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So the problem would be to create and maintain a temperature imbalance (or an imbalance of some other kind) without using electricity. The system would essentially have to reverse itself during the winter, when ground temperatures are higher than air temperatures. Electric pumps do this, creating a pressure differential.

Ground, water, air.

Burying a pipe would work (unlikely as the system will be inside an existing TINY greenhouse). Or burying ONE of the tanks a foot or two down. Cold air sinking wouldn't be a problem during the winter but might during the summer. So if I bury one tank two feet down (it would create a much smaller "planting" space in the higher tank since the water levels would even out) and paint the bottom of the other tank black, one would draw during the winter and the other during the summer.

Maybe.

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Lauren Ritz

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Nathanael Szobody wrote:You could have a windmill circulate your water.

Good idea if the tanks were outside. I wouldn't even need to convert to electricity, just have a double system, horizontal movement. Windmill blades turn another blade under the water.

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Caitlin Mac Shim

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Just wondering - are you planning I’m putting fish in there? If so the windmill blade idea could also help with oxygenation (from the agitation). I’d be careful about not warming the water too much if there’s fish.

This is a really interesting idea, please keep us posted if you give it a go!

Lauren Ritz

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Yes, the plan is to have fish in one tank and plants in both. The plants in the "fish" tank would be those that need the higher levels of nitrogen. I'm also considering duckweed in that tank, since some fish will eat it and it grows quickly. It can also be used for a protein supplement for chickens. The second tank would be used temporarily for fry until they're large enough to go into the main tank.

But it all relies on being able to create passive water circulation.

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R Scott

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You will need a LOT of oxygen or only a few fish. You can get the circulation with a bubble pump if you can figure out a "passive" air pump.

The only power free aquaponics I have seen was in Africa and village boys took turns pumping the water by hand. They had a cistern so it would keep circulating overnight, but someone had to pump a couple times a day.

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Kenneth Elwell

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Lauren, I do think that you are underestimating the oxygen needs of the fish. I've researched (but not built my own) aquaponics systems, and this is a big thing to worry about. Many systems do all of the circulation and aeration using just one pump, but if that fails, or the power goes out, the fish have hours not days to survive.
The thermo-siphoning system you describe, if it circulates much at all, will do so very gently and may not do much for aeration. In a pond, the wind is disturbing the surface and making ripples increasing the surface area, rain is doing the same.
You plan for plants in the the fish tanks, but there's no mention of any other growing beds, that may not provide enough cleaning capacity for the water and the fish. The plant area is often 3-4 times the surface area of the fish tank...
The fish may eat up all the plants and duckweed especially in their tank... Duckweed is amazing, and grows/reproduces quickly, but not as fast as the fish can eat!

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Caitlin Mac Shim

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From my understanding (and it’s only from research, not first hand experience) the usual set up is to have a tank for the fish, and a grow bed for the plants. The grow bed has a medium in it that can both anchor the plants and also provide a home for the bacteria which break the fish poo down into plant food. Then some sort of pump can be used to pump water out of the tank, and then it trickles through the grow bed, and back into the tank, being filtered along the way. It can be a continuous trickle, or a periodical flood, but it needs to be a certain amount of water over a certain time (calculated on the number of fish and size of the grow bed). So, the fish feed the plants and the plants clean the water for the fish.

The most vulnerable unit is this system is the fish. Too many fish and not enough growbed (or not enough water going through the growbed), and the fish suffer from dirty water. Not enough oxygen, or if the water gets too warm, the fish may not cope. If there’s not enough fish the plants will start to suffer from a lack of food, but that’s much more easy to rectify and not as time sensitive as the fish. So, you gotta work to your fish.

It’s fine to have plants in the fish tank too, but these can’t filter the water enough on their own in such an intensive setup. Also, I reckon you’d probably need additional inputs of fish food of some sort in an IBC size tank. I’ve heard of people doing it just feeding the fish on algae in the tank but that was a swimming pool sized set up and lightly stocked so it achieved a natural balance over time.

Also, enough plants to feed the fish exclusively in an IBC size tank may have a detrimental effect on oxygen levels in the water. Again, I’m not speaking from Experience here but I’d definitely think it was something to check out.

I reckon an electric free system could well be achievable with a windmill. One that would continuously pump water from the bottom of the tank, through a grow bed, and then position the edge of the grow bed high up over the fish tank so it trickles in from a height back into the tank and oxygenates the water.

There’s some interesting bamboo style water wheels that have been traditionally used in Asia that kind of keep themselves going in perpetual motion if you know what I mean? I imagine something like that could work? Although I think they scoop water from the top levels of the tank rather than the bottom (where the poo drops).

But yeah - biggest factors in all this are the fish, caus in such a small space they are very vulnerable to any kind of environmental changes (temp, ph, oxygen, disease). The variety of fish matters too, in that different fish grow better at different temperatures, and produce a different amount of waste depending on their rate of growth over time etc.

I’ve been trying to dream of electric free perpetual water pump systems too, so am really interested to keep up with your project!

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Low Oxygen levels may not be a detriment if the right fish species are used, bottom-dwelling fish such as basa and other catfish species could theoretically survive in a low O2 environment.

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Dylan Urbanovich

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Another issue is going to be getting the water to the grow bed. unless you are growing aquatic plants you're going to need to cycle water through the grow bed, usually, this is achieved with a bell siphon in the grow bed. Unfortunately, a bell siphon requires water to be pumped into the bed. I'm not able to think of a way around this problem using just gravity and thermal differentials.

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Carla Burke

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Unless maybe the plants float in a flatbed 'barge', with a screen bottom. I'm sure there has to be a way. I used to live in a couple different rentals owned by farmers who started their tobacco in greenhouses, in styrofoam barges, floating in ponds in the floor. I'm sure there must be a way to translate that to a permaculture friendly aqua ppl onics system. It's something I've been occasionally doing mental gymnastics on (as opposed to actually doing anything about it) for quite some time. I'm not ready mentally or physically, yet, so I haven't begun to dedicate the funds to experiment. But, I know I've no interest in styrofoam, and have thought about mini pontoons, instead. The screen (from whatever material is chosen) would have to be sturdy enough to contain the plants and growing medium. Low oxygen-guzzling fish, possibly including the aforementioned, plus mussels, crawfish, snails, and shrimp are all possibilities. The mussels also come with the bonus of doing a great job of cleaning up ponds.
In addition to the floating crops, things like cattails are also hard working eco- boosters.
The advantage to the totes, while they are a material is rather not increase usage of, is they would make harvesting both the plants and the critters much easier, and, set in the greenhouse, would become year- round food sources, as well as providing humidity for other plants in the greenhouse. I know i'm preaching to the choir, lol. It's just something I'm really itching to figure out. Maybe we can all find our own best paths, by getting all the ideas out there, that we can.

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Nathanael Szobody

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It seems the issue is not the physics, but the scale. Aquaponics is intensive. Natural, passive energy is not. Natural waterways circulate passively, but they use enormous scales to do it. How many gallons of lake water support each of the fish therein? Your passive warm/cool circulation could work in your totes--if you're looking to support a couple goldfish and a basil plant. It seems that for adequate circulation for anything more serious (that is, intensive) you need mechanical help, like a windmill.

For oxygenation particularly, you could circulate the water through several other totes that are chock full of water plants. In other words, you sacrifice some of your nutrient in order to produce oxygen. It's all a question of scale. You can't grow lots of fish on a little bit of oxygen. Even if you find something that can survive on lower oxygen levels, how healthy will they be really?

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This is a little like the design of natural swimming pools. A segregated area of the pool has plants that clean the water and return it to the main pool. Even these tend to have a pump of some kind to circulate the water.
I was wondering if a capillary mat might work, but then the water is consumed by the plants, not returned....
If the fish need continual aeration (and oxygenating plants are not sufficient?) and an external energy source is required, then you will probably need either a continual source of external power, or an energy storage medium of some kind.
Is there any particular reason that you don't want electricity? A small bubbler in a column with a solar cell and reserve battery would be a relatively easy way to go. Any other solar heat system would only work while the sun shines.
Water powered could be a possibility if you had continuous running water. Either ram, or paddle wheel/coil, or other gravity would be simple and electric free as long as you had running, non frozen water. It wouldn't need to be clean, since it would not be not in contact with either plants or fish.
Wind power, again only works while the wind blows, unless you combine it with a separate energy storage like a water reservoir that then run a water pump as above.
How often would you visit? Would it be practical to have a human powered energy storage, lifting a weight as you open the door for example? That would be two lifts everytime you accessed the greenhouse, although it would make the door heavy. That weight could then be released to run a pump system somehow.
I'm inclined to a bubbler myself. In a tube it would make a current as well as aerating the water, so could suck it away from the cleaning plant ponds, but I don't know how to make bubbles without an electric pump. I guess it's no different to a bicycle pump though, so should be possible. Air is easier to move than water....

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Lauren Ritz

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At this point I am just trying to intellectually work out passive circulation, getting the water from the "fish" tank into the other where the nutrients can be used by the plants. Everything can be done, it's just a matter of figuring out the processes, and thank you for all the input.

If I can work out all the details I will be doing a form of Kratky hydroponics with the fish providing the nutrients, so oxygen for the plants won't be an issue. Oxygen for the fish is something I hadn't considered yet, but again it appears to be doable if I can figure out the passive processes.

I choose not to use electricity for a number of reasons. All of my projects are as low input as I can get them, preferably 0 (and yes, I know that is unlikely) which is part of why I started working with Kratky in the first place. It requires no pumps, and no electricity. I don't generally use lights or mats or special soils for seedlings and so on. I also want to avoid either mechanical breakdowns or supply chain issues. To the extent possible, everything I do is sourced from my home area and at $0 cost.

Choosing the right fish and the right plants would be important (right now I'm wondering about rice, since it oxygenates the water around the plant), as well as all the other things that have been brought up. I have several other projects to complete before I can focus on this one, so I have time to put everything together.

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Lauren Ritz

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Carla Burke wrote:Unless maybe the plants float in a flatbed 'barge', with a screen bottom. I'm sure there has to be a way

I will cut the tops off the IBC totes (waste stream), turn them over and punch holes in the bottom for the net cups. In that sense it would act just like hydroponics. I've been experimenting with Kratky hydroponics and natural nutrients for a while. I'm confident it can be adapted to this kind of system.

Carla Burke wrote:Low oxygen-guzzling fish, possibly including the aforementioned, plus mussels, crawfish, snails, and shrimp are all possibilities. The mussels also come with the bonus of doing a great job of cleaning up ponds.

I do plan to put something in there to clean the tanks. Thank you for the ideas!

Carla Burke wrote:It's just something I'm really itching to figure out. Maybe we can all find our own best paths, by getting all the ideas out there, that we can.

This. Yes. Not all my ideas will work, or work as planned, but with enough brains added to the pile something can usually be worked out. There is always a solution.

Actually I just had an idea for an underwater bubbler. Another thing to think about.

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Mark Reed

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I would be very interested in this but unfortunately in prior research and efforts I came to to the conclusion that it isn't possible. Something has to provide the energy to move the water, it just isn't going to cycle by itself by any means that I know of, if you do come up with something I would love to know!

My little pond now relies on an electric pump and although I hate it, I just can't figure an alternative. I am considering trying to replace it with solar or wind but it still a pump and would only run intermittently. Of the two wind is most attractive to me as at least it is just mechanical rather than electric.

I did come across one completely goofy idea of encouraging evaporation. Then capturing and condensing the evaporation in some type of overheard apparatus and channeling it back where needed by gravity. I judged that on top of the fact it probably would not work, any such apparatus would about have to be absolutely stupid looking.

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I think you could stock the tank with carp of some kind, goldfish, or koi for example, and let them be.
In the absence of inputs (other than sunlight), they will probably do ok.
Algae will grow, they will eat it and the oxygen levels will be what ever they are.
Carp are edible, even though they are seldom valued highly in the US.
Without inputs, the density will be low, but maybe that's ok?

Another thought, amphibians.
As polliwogs and tadpoles they will be small, aquatic and omnivorous, as they mature they become large enough to eat, air breathing and carnivorous.
This bypasses the oxygenated water bottleneck.
It does create a need for more animals to feed them.
Pests are the obvious resource, cannibalism works as well, plus , if you keep chickens nearby, the emerging frogs and toads become self dispensing chicken feed, and you needn't worry about feeding them as adults.
Hopefully there will be survivors and they will procreate.

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Lauren Ritz

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William Bronson wrote:I think you could stock the tank with carp of some kind, goldfish, or koi for example, and let them be.
...
Another thought, amphibians.
As polliwogs and tadpoles they will be small, aquatic and omnivorous, as they mature they become large enough to eat, air breathing and carnivorous.
This bypasses the oxygenated water bottleneck.
It does create a need for more animals to feed them.
Pests are the obvious resource, cannibalism works as well, plus , if you keep chickens nearby, the emerging frogs and toads become self dispensing chicken feed, and you needn't worry about feeding them as adults.
Hopefully there will be survivors and they will procreate.

Don't have chickens yet, but that's a great idea! I was thinking of feeding the duckweed to chickens, but frogs would probably work just as well. One more thing to consider. :) I'm getting quite a list. Thanks!

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A while ago I remembered that during the summer last year I was trying to work out a way to passively keep my hydroponics tanks up to the right water level, and I tried one of those plastic milk bottles. The bottle was completely sealed, no water leaked when I tested it, but when I put the hose down in the water it drained immediately. Apparently the bottle was sealed enough to keep water from getting out, but not enough to keep air from getting back in.

I'll have to test it some more and see if it will work as an underwater bubbler.

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Now the thing you are missing is the temperature change per day the fish will stand without harm. It is something like 1 degree per day. The fish will have some temperature range they can live in. Usually about 15 to 30 degree range. But if you move the temperature by that much in a day the fish will be harmed or killed. The amount of change you can have in any given day is a tiny fraction of that unless you want to make the fish sick or kill them. Of course even if you could swing the full temperature range you are dealing with a really complicated system for it to work and the amount of fluid you can move passively is really small. Likely not enough to support a single gold fish. So the answer to your question I am going to say is NO.

Now a no moving parts system is possible under very special conditions. If you had at least 3X the fall vs your lift height of a constantly running water with enough flow volume it could be done. Use the falling water to power a Trompe pump to make air pressure so no moving parts there. Run that thru an airline to an airlift pump and you have a system that will run with no moving parts. The catch is the amount of height and large constant flow needed to make it work. If you want to lift say 10 feet then the air pump will need to be at least 15 feet deep. To achieve the air pressure needed to drive that the trompe pump will need roughly 30 feet of fall.

So far as I know this is the only no moving parts system that will allow true aquaponics.

Now there is a neat you tube video discussing why an airlift pump would be a better answer for aquaponics. But they are still driving it electrically. And the ways to make air pressure have more options but they are all complex in some form.

Right now low voltage magnetic drive pumps are the other pump choice I would be looking at. The one I got for the solar collector project has no external moving parts. The rotor for the pump is the armature and it is all inside the pump. No seals to fail. It is a neat little pump with very little to go wrong. And being DC I can run it off solar, off batteries or off AC power with very little trouble trading between them.

Now your other option is eliminate pumping totally, grow plants in the top half and fish in the lower half and fence them away from each other. There are a number of you tube videos on this type of system also. Most of these systems are bigger tanks though so one end of the tank can be devoted to letting the fish surface and feed etc.

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C. Letellier wrote:
Now your other option is eliminate pumping totally, grow plants in the top half and fish in the lower half and fence them away from each other. There are a number of you tube videos on this type of system also. Most of these systems are bigger tanks though so one end of the tank can be devoted to letting the fish surface and feed etc.

I thought that's what I said. Two tanks, tops inverted with plants on them, roots down into the same water the fish are in. I guess I wasn't clear enough. Not planning on "fencing" them away from each other, though. Not sure what you mean by that. One big tank split down the middle? I'm planning on linking two 250 or 300 gallon IBC totes, so technically room for 10-20 full sized fish. The fish will only be in one tank, except for the cleaner fish. Both will have plant rafts and I'll try to choose plants that put oxygen into the water as well as choosing fish that can eat plant roots.

I'm just in the planning process at the moment. When I get to that point I'll start with two or three baby fish and work up, learning as I go.

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I think the reason the fish are fenced away from the plants is caus they can have a tendency to eat the roots.

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So are you looking at basically a big plastic cube filled with water and a plastic tray of plants floating on top of the cube? And this fish live in this cube? Or the fish live in a separate cube below/adjacent to the plant cube?

I have not done aquaponics, but do keep several home aquariums. You are not going to have a healthy environment for the fish without some form of bubbling or agitation to aerate the water in a small, cubicle, indoor system. There just will not be enough individual water molecules encountering new oxygen from the air. Plant roots at the top of the water will not contribute significant oxygen, in fact, plants covering the surface can interfere with oxygen exchange. Submerged plants give off O2 during daylight hours, but not necessarily through the night. If you do not want to connect it to an independent power source, then maybe find a way for the aquaponics system to make use of some excess power from other household sources, or some kind of green power like a small solar cell, or a chinchilla wheel. Or commit to daily manual water change.

Even though your IBC tanks may feel very large, as others have said they are nothing like the scale of a natural pond or stream which would support fish large enough for human consumption.

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Nancy Reading

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Location: Isle of Skye, Scotland. Nearly 70 inches rain a year

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posted 3 years ago

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Could this be an idea?

Apparently the clockwork is from a gramophone...

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Lorinne Anderson

pollinator

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posted 3 years ago

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Is a water wheel an option? Inflow from tank one causes rotation lifting water from tank two back to tank one via a spillway?

Lorinne Anderson: Specializing in sick, injured, orphaned and problem wildlife for over 20 years.

Nancy Reading

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Sorry Lorinne, that sounds like a perpetual motion machine to me.

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Lauren Ritz

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posted 3 years ago

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Caitlin Mac Shim wrote:I think the reason the fish are fenced away from the plants is cause they can have a tendency to eat the roots.

Which is actually something I've been considering. Depending on the circumstances (LOTS of different issues involved!) that could be part of their food.

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Caitlin Mac Shim

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What do you reckon is your main goal with the system? Like, do you hope you grow fish/crustaceans to eat (human consumption), or for feed (chickens/other) or plants for human consumption or animal feed, or is the idea to primarily grow plants to feed the fish, or all of these things? Or is it more a case of figuring out if a passive system could operate and then growing whatever works?

Could something using gravity work? Like a drain in the bottom of the tank, which you can release to flush out some poo heavy water from the bottom, and the drop in water level allows fresh water to flow in at the top? As long as you didn’t replace too much water at once it shouldn’t be too much of a shock to the fish.

It’s not achieving circulation (without coming up with a way to clean and return the water to the top), however it would give you nutrient heavy water to use somewhere else, and if you had enough water catchment to feed the system, then the re-circulation of cleaned water might not be so necessary. Would depend a lot on water availability I guess. Aquaponics are often utilised to address water scarcity, but if you have plenty you could set it up as a kind of fertiliser production system?

There’s still the oxygen thing, but I’ve seen carp living in a big ceramic pot with a couple of plants. They could probably manage fine as long as you didn’t want them too big (or too tasty lol).

I keep trying to imagine some kind of Esher image involving tanks endlessly trickling water into each other round in a big circle

Lauren Ritz

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Caitlin Mac Shim wrote:What do you reckon is your main goal with the system? Like, do you hope you grow fish/crustaceans to eat (human consumption), or for feed (chickens/other) or plants for human consumption or animal feed, or is the idea to primarily grow plants to feed the fish, or all of these things? Or is it more a case of figuring out if a passive system could operate and then growing whatever works?

Everything I do has to be low input, local, and no electricity or gas. It must also provide some kind of benefit, whether that's food for me, food for plants, whatever.

I started imagining how a passive aquaponics system might function and kept coming up against the electricity thing. Pumps and filters are entirely out. I don't work that way. So alternatives. I came up with two that I think are workable to get circulation between the tanks and there are a couple more good ones in the thread. The experiment until it works thing is pretty much me. Somebody tells me it can't work I just go to work and (often) prove them wrong. : )

My goals, definitely human food (plant and fish). I can do the plants, no problem. But fish need other things. Circulation was the first one I decided to address, and here we are.

Caitlin Mac Shim wrote:Could something using gravity work? Like a drain in the bottom of the tank, which you can release to flush out some poo heavy water from the bottom, and the drop in water level allows fresh water to flow in at the top? As long as you didn’t replace too much water at once it shouldn’t be too much of a shock to the fish.

It’s not achieving circulation (without coming up with a way to clean and return the water to the top), however it would give you nutrient heavy water to use somewhere else, and if you had enough water catchment to feed the system, then the re-circulation of cleaned water might not be so necessary. Would depend a lot on water availability I guess. Aquaponics are often utilised to address water scarcity, but if you have plenty you could set it up as a kind of fertiliser production system?

I live in a desert, so water is certainly not plentiful. There are drains at the bottom of the IBC totes, so that kind of setup isn't out of range. The fresh water in that case would be put in the tank with no fish, so it shouldn't shock the fish as it would take a while to mix. The leavings in that case would probably go right back into the soil in the greenhouse.

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Caitlin Mac Shim

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posted 3 years ago

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So how about gravity feeding them by siphoning from the outlet at the bottom, into the top of the next tank, continuously? Would that work or does a siphon HAVE to have the outlet point lower than the inlet? With the right kind of pressure water can go uphill sometimes right...?

Possibly - you have your ‘dirtiest’ tank, with the bigger fish, and have a hose from the bottom outlet which siphons continuously into the top of a tank chockers with oxygen producing water plants that double as fish food when they’re over growing. Their main purpose is cleaning the water, but you harvest them for fish food when you need to thin them out. Only crustations that won’t eat the plants (but will help clean out the poo) in here. Then that tank continuously siphons from the bottom into the top of a third thank with a mix of plants and baby fish. Then that tank continuously siphons from the bottom back into the first tank, topping it up with cleaned water.

As all the tanks are the same size, and have roughly the same amount of water, they should have roughly the same amount of pressure (weight) pushing the siphon, and therefore be draining/topping up at the same rate. So it creates a continuous current between the tanks powered by the weight of the water? Does that make sense or am I tripping...?

Possibly I’m confusing how a siphon works

And I appreciate that if it was that simple it would probably have already been done.

But if you COULD get it to push uphill, then the trickle from the hose could also help oxygenate the water a bit...

Lauren Ritz

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Caitlin Mac Shim wrote:But if you COULD get it to push uphill, then the trickle from the hose could also help oxygenate the water a bit...

The siphon could keep going indefinitely as long as the end of the hose is lower than the start and both are in the water. That way there's no need to have pipes between the tanks, the water gets mixed and oxygenated simultaneously (if mildly) and no pumps! All the tanks would need to have essentially the same water level and it's a much larger system, but well worth exploring.

You're a genius! : )

With the fish tank draining directly from the bottom (rather than a siphon), it will create a continuous current of the dirty water into the plant tank, then siphons from the upper level of that tank (clean water) into the next.

So a number of things to test, but I think we have a possible solution!

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Caitlin Mac Shim

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Woohoo!
Please keep us updated with what you end up trying, it’ll be really cool to see how things work

Nancy Reading

steward and tree herder

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Location: Isle of Skye, Scotland. Nearly 70 inches rain a year

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posted 3 years ago

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Lauren wrote:

it will create a continuous current

Lauren, You may be adding something here that I'm not aware of, but although the levels in tanks linked by a syphon will even out. I don't think the water will flow unless there is a disturbance. According to Newton's first law of motion:Newton's laws of motion If you are topping up the water in one tank, or the evaporation in another is higher, then the water will flow in the direction to even it out. I'm not sure if you can even control the glow to be one way unless you have a valve in the pipes.

Can you sketch it out?

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Lauren Ritz

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The siphon will always flow toward the longer side of the hose. The effect is created by a vacuum (in a sense) at the peak of the siphon. The "inflow" must always be higher than the "outflow," or the siphon won't work at all because it needs the drop in order to maintain that vacuum. When the water level on the inflow side gets lower than the siphon, the siphon stops. If it doesn't get lower, and the "outflow" remains unobstructed, it SHOULD continue flowing.

It will require testing, of course, but the laws that govern a siphon are gravity and air pressure. You're thinking of the two tanks as one unit because of the siphon, but they're technically not in the sense of the physical rules governing the behavior. If they were linked by a pipe below water level, yes, they would even out, but other forces are working on the siphon. It's possible that other rules I'm not considering will eventually (or even immediately) stop the siphons from running. It's possible that the water in the receiving tank needs to be so low as to make it inoperable. It's something to test, and I may need to make adjustments.

Rocks will not end up back at the top of the mountain after a rockfall, or the water end up back at a lake after running down to the sea. At least not in the same form. The force pushing the system in this case is gravity.

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John Rosseau

Posts: 87

Location: Northern Ontario

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Okay, an idea that may or may not be worth building on...

With the use of pumps and electricity out, would the use of a hydraulic jack be acceptable? It would be manually operated.

I am imagining using the jack(s) to raise a tank up over another and allowing water to flow from one into the next, it could go through a passive aeration system. Something utilizing this sort of gravity driven aeration concept, but on a smaller scale to allow for a slower flow of water:

Once one tank has nearly emptied into the next, it could be lowered, and the processes repeated on the next tank. Of course the interval of this would have to be worked out... 1x daily, 2x daily, 10x daily?! It would depend on a lot of factors.

A full IBC tote can weight up to 2,600 lbs, so it is heavy, but it is not difficult to find hydraulic jacks/lifts that could handle this with ease.

edit - if the tanks were connected via fulcrum, think see-saw, it would take much less effort to raise one relative to the other, something to think about maybe...

Hand crank could work also.

Lauren Ritz

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Lots of possibilities. It's one thing I like about the brainstorming phase of a project--NOTHING is off the table! :)

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