Water Quality and Harvesting Nutrients
Plants are able to cure any water quality problems that may develop, in a pond that is based on a clean incoming water supply.
Various sources of pond wisdom, suggest that for optimal cleanliness, about 60% of the surface should be covered with emergent or floating plants. This leaves 40% available for swimming and boating. Ponds that have too much open water, tend to grow lots of algae.
A multitude of chemical remedies exist for those silly
enough to buy into the idea that a farm pond needs to be crystal clear. Some poison the water, some dye it to prevent solar penetration, some put in UV light "sterilizers" and some hire consultants with a dozen more ideas. ---- A few, more evolved pond owners accept algae as a normal part of pond ecology and they leave it alone to be managed by creatures that eat it. They carefully control nutrient inputs. I'm in that camp.
Harvesting Nutrients ---- None of the dozens of videos that I've watched suggest that nutrients should be gathered both as a way to fertilize the land and to control algae bloom. ---- This is probably because most information on the subject concerns production of large mouth bass. Some go to great lengths in labor and expense, to grow trophy sized bass. They buy feed and structure long food chains around bass. For instance, it takes about 10 lb. of blue gill feeder fish to put a pound of meat onto a bass. I'd rather eat 10 lb. of little blue gill. ----
Back to nutrient harvest ---- Filamentatious algae fix nitrogen. The only known limiting factor to their growth is phosphorus supply. Extreme eutrification is a common problem in natural waterways that are inundated with phosphorus rich agricultural or municipal runoff .--- I will add rock phosphate in amounts needed to foster a suitable level of algae growth so that flotsom can be continuously gathered. Everything gathered from the surface will be offered to livestock and the leftovers used as
mulch or for other soil improvement.
Bottom Muck ---- The deepest area of a pond tends to accumulate a gooey mess of rotten plants and other sediments. As this material decays, it consumes dissolved oxygen. When I look at the huge amounts of aeration required to break this stuff down it is clear that this is an area where most ponds could use some management. I will regularly vacuum up the bottom muck. This muck is high in nutrient value. When plants grow in water, they release oxygen. When they decay they consume oxygen. By gathering
organic matter before it rots, I will be causing a net gain to my oxygen supply. The dreaded filamentatious algae can cause extreme oxygen depletion when large masses decay. But if it is harvested regularly, it contributes oxygen to the pond. Every bit of
carbon in their cells came from CO2 in the air or in the water and oxygen was released during that growth. Harvesting both dead and living plants moves the oxygen uptake part of the cycle to dry land so that those materials cannot draw on dissolved oxygen supplies as they decompose.
The ponds will produce a net gain in nutrient to the farm, due to the nitrogen added by algae and other nitrogen fixers. The plants will produce a net increase in oxygen available to the fish.
Agents of Decay --- When bottom muck is vacuumed up, many little worms and other things that eat detritus will be sucked up with it. There is a whole community of critters similar to those that break down forest litter on land. This protein harvest will be eaten by the
chickens when the mucky water is broadcast onto soil. Tiny creatures that wash into the soil will enrich it. It won't hurt the pond to loose these creatures. They reproduce quickly. Any shortfall in these populations would tend to slow decay which would in turn, slow the loss of dissolved oxygen to those processes. They all breathe oxygen. I'm likely to remove less than 10% during any single day's cleaning.
Seaweed ---- It's easy for me to gather an abundance of seaweed which contains many nutrients. Some of it will be eaten by fish and bugs. The addition of salt and seaweed are often prescribed to enhance fish health. This means there will be no need to wash stuff that is gathered. My soil is salt poor, so no problem there. Water used for irrigation will contain nutrient from the sea.
Tree leaves, twigs, bird feathers and many other organic materials are likely to find their way into a pond. Most of them float and are easily driven into concentrated mats when the wind blows. They are easily netted with a fine mesh as is used for cleaning swimming pools. If they sink, the vacuum will eventually get them but in the interim, they consume dissolved oxygen.
------------------------------------------------------------------------------- A few hours later I have returned with more
Aeration --- Much of the preceding verbosity was concerned with methods of preventing loss of dissolved oxygen to decay processes. This got me thinking about how much electricity would be saved in a pond that can do just fine with little or no aeration. I Googled things, this way and that and found the weight of carbon dioxide. CO2 is 27.3% carbon and 72.7% oxygen. --- 72.7 divided by 27.3 = 2.66 ---------------- One pound of carbon requires 2.66 pounds of dissolved oxygen to be completely gassified. This means that if I remove leaves and sticks containing 10 pounds of carbon, I have just saved 26.6 pounds of oxygen. --- I will next consult Mr. Google to see how many hours various units would have to
pump air into the pond to add that much oxygen. ------------ and I'm back------- Commercial fish farmers comparing aeration to using bottled liquid oxygen, seem to agree that it costs about 1 kilowatt hour of electricity to add a pound of oxygen to cold water using the latest aerators. More aeration is required for warm water. That kwh of power is worth about 10 cents here in B.C. and much more in other places. If a generator produced that same power, it's likely to cost more than 50 cents per kwh. At that price it's going to cost $1.30 to remove a pound of carbon through aeration. ------
but we're not done spending money ------- The equipment must be bought and maintained. If a $500 generator consumes $500 worth of gas and then it dies or is stolen, you paid $1000 for the power that the machine produced. I've had such bad luck with generators failing or being stolen that I figure they have cost me $10 per kwh when amortized over the few hours of service before tragedy struck.
That was a lot of math. Now here's more. I'm never going to run down to the pond to remove a pound of carbon waste. I'm going to do it 100 lb at a time but not every day. You might have to remove a ton of flotsom to get 200 lb. dry weight, which would be half carbon. That might take an hour when done from a little barge. I can't see ever getting my aeration costs below 25 cents a pound, so that ton of algae, leaves and sticks is worth $25 in savings. After being allowed to drip out, the material would be loaded by hand or excavator or crane arm, onto the truck and driven a short distance to wherever chickens or pigs are eating that day. It's going to have some unknown value as feed and some other unknown value as fertilizer. ---------
AND THAT'S HOW THE REMOVAL OF CRAP FROM A POND CAN TURN INTO A MATH LESSON --- the test is on Tuesday.
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