Conversation about Aquaponics

Copper can be toxic to fish.

The difference between hydro and aquaponics is what all is being raised. Hydro, just plants on liquid diet. Aqua, fish too. The aquaponics systems I work with look like giant bunk beds. We are doing it in a greenhouse in the middle of an economically depressed neighborhood in the city. We dug down about 6-7 feet in the floor of the greenhouse, and built a pump that takes the water from a few big barrels where its aerated, down to fish, up to two layers of veggie beds. They're just sandy and pebbeley and thats what we use to grow our veggies... We have tomatoes in it, and swiss chard and water cress.


The other one is exactly the same except instead of beds, theres 6 rows of 3 layered boxes that we stacked in a staggered fashion on top of one another. Filled with soil, we can direct sow and everything into them. The way the boxes are stacked makes it possible to have 4 plants growing in one box. The water has to be strained a little better with the pump system because we have it trickling down through very small tubes that get easily clogged

I think what still trips me up is the inputs that are required.  Duckweed has a high protein content but its dry weight that is 45% protein.  It's mostly 90% water so to make enough feed to supplement in a meaningful way you would need way more space than is available for most people.  Maggots can drop your feed requirements significantly 50% or so if your really good.  But that still leaves a large amount of protein and calories that are coming from somewhere else.  And from what I see on the aquaponics sites that I frequent is that almost every person doing it uses commercial fish feed and those that aren't don't get very good growth.  And the only reason that fish food can exist is because we are stripping the ocean clean and any critter that isn't commercial viable by itself gets ground up and mixed with some grain and sold as feed. 
This creates the illusion that your growing in a very small efficient space, but your using acres and acres of ocean and field to grow that food. 

As you improve your soil your inputs decrease significantly.  As your improve your aquaponics system your fish needs stay the same your beds can improve.  Your inputs stay the same for the most part. 

jbreezy wrote:

This creates the illusion that your growing in a very small efficient space, but your using acres and acres of ocean and field to grow that food.  

Buying fish food isn't necessary, in my opinion.  But that's just based on opinion, not experience yet.  If you're still somewhat interested in aquaponics, maybe you could pioneer a low-impact system made of recycled and sustainable components,with home-grown fish food. 

My first aquaponic salad; lettuce and chard     :

Cool.  Got any pics of your system?

Here's my present layout:



Still a work in progress. 

Looks good!  I'm very interested to hear how you go with turning your opinion into experience, re: generating most of the fish feed on site.

A very crude energy analysis on this to figure out how much food growing space would be needed to produce 50 fish each 6 months is below.  The estimation it gives is that fish food growing for this system might need something around 13 square metres, give or take.  This certainly seems doable, unless of course you have your aquaponics setup on a balcony or something.

100 fish/yr x 500 g harvest weight = 50 kg total harvest per year
50 kg x 1.5 feed conversion ratio = 75 kg feed

Assume 11000 kJ per kg of food

Total food energy required = 75000 x 11000 = 825000 kJ = 229 kWh

Assume we can capture 2W/m2 of energy into food products 24/7.  That gives 17.5 kWh per square metre per year.

What kind of fish food is one growing which takes 13 square meters? 

I used a standard figure for capture of photosynthetic energy per square metre.  What you actually grow will vary the real space required.  13 m2 is probably on the low side.

It was really just a rough exercise to figure out if the area would be in the tens of square metres or hundreds of square metres.  If it is hundreds of square metres then jbreezy could be right in his comments.  But it seems possible in a smaller space.

Thanks!     My plan is to raise Red Wigglers and Black Soldier Fly larvae on "waste" from the household and garden.  I also plan to collect "free range" Pillbugs and Sowbugs from my garden.

We'll see how that works out!   

Yeah, that method would obviously reduce land area needed, as waste is a separate resource from existing processes.  Kills 2 birds with one stone.

Here is an update on my project.. Also wanted to add that dry weight vs "wet" shouldnt make a difference on the duck weed, the protein content should still be the same. Also duck weed grows so fast that you can raise it in shallow pools, harvest it every few days and freeze it in blocks to feed over winter. You also have all of the scraps from the system to feed year round.

Drying the duckweed would increase the proportion of protein in the duckweed (by reducing the amount of water), giving a higher protein% which is what I think jbreezy was trying to say.

Manitou, how much duckweed would you feed per day roughly, and how much pellets/scraps/other?

Well it depends on how many fish you have, but generally as much as they can eat in 10 min or so and as often as they will eat that way.

Right, what I was trying to get an idea of how much pellet feed can be reduced by when feeding duckweed...?

Well I dont use pellet feed at all Just duckweed, garden goods and bugs. So I gues my answer would be completely eliminated. But I am also not concerned with high production, only with a natural self producing system.

Very cool.  Can you show us any photos of your system & give some info about what fish, how often you harvest, etc?

I am making a youtube video of the new system and will share the link here

Fantastic, look forward to seeing that, thanks!

I've been thinking a lot about the feed issue since I'm moving to a new place and will be setting up a new AP system.

I keep coming back over and over again to the Aztec chinampas system. Plus add in other closed-output systems like worms and BSF larvae.

I think it could be a very-nearly closed system.

is it possible to do the following:

(1) build a swale out of the side of a slope in order to create natural spring line down the hill,
(2) dig out a volume controlled pond at the spring line and just above the surface fix your tables around the pond for an aquaponics system.
(3) then build a geodesic dome surrounding the system to protect from floods... will a spring line keep a body of water steady to use ebb and flow tables with?

Sounds more like a keyline dam than a swale, but it sounds feasible. You'd need a catch pond at the bottom to recirculate the water back to the top of the system.

yes a dam, not a swale sorry.  sweet... I will have to work on this

Has anybody tried to add adya clarity, or black mica to their system? supposedly this mineral will keep bacteria low for a long, long time and I wondered if it has ever been applied to aquaponics

Bacteria are the foundation of aquaponics. Why would you want to keep them low?

Hi all,

I don't know if this link has been shared, but there is some good information to be found http://gardenpool.org/

The person is growing chickens, fish, and food all in an in ground swimming pool. He uses the chicken manure to cause and algae bloom, which is then eaten by the tilapia. The tilapia waste is then used to grow vegies and returned to the pool through the grow bed filter.

I just finished my first year of aquaculture a couple of weeks ago. I raised some blue tilapia from fry to harvest using a 120gal aquarium to start then transferring to a 8' inflatable intex pool in my yard for a grow out tank. The system was very simple and only used a sump pump and a biofilter. I floated rafts with lettuce on them as an experiment, it went well. Next year I plan to expand the system as well as the grow beds. I feed my fish mostly pellets, as much as they would eat in 10min. At least once a week I would overfeed the fish, this would cause an algae bloom and the water would look like pea soup. Tilapia have the ability to filter algae from the water with their gills to use as food. This comes in handy for the pregnant females who can't eat, they are mouth brooders. The "pea soup" can be controlled by how much you over feed, as well as how much light you let hit the water. After a day or two for pea soup I would use the sump to drain ~30%-50% of the water, watering my veggies with it, then refill.

Next year I plan to have a dedicated algae pond, as well as a dedicated duckweed pond. By using manure, from my rabbits, to grow algae and fish ammonia to grow duckweed I hope to be able to reduce my feed costs substantially. Hope this info is useful to anyone.

may have misspoken, but look at what it does to this pond... you can scroll through the video bc it is long so I will give you a summary... it shows them putting black mica in a pond and the mica ridding the water of pollutants in 10 minutes.

There aren't any "pollutants" an an aquaponics system, so there would be no need for that product. 

I dont know maybe your right... I wonder if anybody has tried it.

Neal McSpadden wrote:
I've been thinking a lot about the feed issue since I'm moving to a new place and will be setting up a new AP system.

I keep coming back over and over again to the Aztec chinampas system. Plus add in other closed-output systems like worms and BSF larvae.

I think it could be a very-nearly closed system.

I also have been mulling over the idea of incorporating a chinampa system. I would like to be able to fence it and use it as a paddock system for the ducks I will eventually get. Maybe even use the land area in between as a rabbit / chicken paddock. Being on a semi island might keep the rabbits from burrowing away.

is it possible to hook up the tanks to a well pump? how much water needs to come in?

thank you for sharing

Perma Republican wrote:
is it possible to hook up the tanks to a well pump? how much water needs to come in?

thank you for sharing

I believe the recommended water change for a recirculating aquaculture system (RAS) is 10% of the volume weekly. This could change based on stocking density as well as filter capacity. I had my sump hooked up with a float valve from the hose to make sure there was a constant water level. The only reason I drained mine ~30% - 50% was to water my veggie plots, approx.  1500sq ft worth.
An 8’ dia pool filled 2’ deep holds about 750gal or 100 cu feet.  I have read stocking at 1lb of biomass to 1 cu foot of water is a good rule of thumb, but again there is a huge amount of variables to consider.
Next year I plan to run drip irrigation to my plots and run the pump on a timer, with that combined with the auto float valve from my hose I should be able to automate my water changes.

Brad Davies wrote:
I also have been mulling over the idea of incorporating a chinampa system. I would like to be able to fence it and use it as a paddock system for the ducks I will eventually get. Maybe even use the land area in between as a rabbit / chicken paddock. Being on a semi island might keep the rabbits from burrowing away.

That sounds like a great idea.

Brad Davies wrote:
I believe the recommended water change for a recirculating aquaculture system (RAS) is 10% of the volume weekly. This could change based on stocking density as well as filter capacity. I had my sump hooked up with a float valve from the hose to make sure there was a constant water level. The only reason I drained mine ~30% - 50% was to water my veggie plots, approx.  1500sq ft worth.
An 8’ dia pool filled 2’ deep holds about 750gal or 100 cu feet.  I have read stocking at 1lb of biomass to 1 cu foot of water is a good rule of thumb, but again there is a huge amount of variables to consider.
Next year I plan to run drip irrigation to my plots and run the pump on a timer, with that combined with the auto float valve from my hose I should be able to automate my water changes.

A lot of people have found drip irrigation to be a problem with an aquaponic style setup. The drips get plugged up with bio-slime (technical term ).

I think you'd have to filter the water first before running it through drip tubes, even if it's been filtered through a grow-bed, the water seems to have a pretty large quantity of particulates.

H Ludi Tyler wrote:
I think you'd have to filter the water first before running it through drip tubes, even if it's been filtered through a grow-bed, the water seems to have a pretty large quantity of particulates.

I agree the water would have to be filtered for solids first. I plan to have the water get drawn off from the system after it has been through the solid seperator, but before the bio filter / grow beds.

I wonder if Tilapia eat moths... either way, what if you could hand a light attracting bug over the tankk

PermaRep, that's an idea my husband has had, to be installed once we get the fish.  He thinks there should be some kind of downward-facing baffle over the light to direct the moths into the water.    I wonder if a little fan could be included to whack them down if they don't naturally fall....

or shocking them somehow so they drop in