I'd like to run an aquaculture idea past you guys and see what you think of it:
Instead of aquaponics in which the plants are in a separate container, what about a single large tank with a screen across, with planting tubs of useful and edible aquatic plants like taro, duck potatoes, etc. on one side, and fish on the other side of the screen? My theory is the aquatic plants would clean and oxygenate the water but the screen/fence would keep the fish from disturbing and eating the plants. Some edible critters like crawdads or freshwater clams might live on the plant side.
Is there are downside to this scheme I'm not seeing? Do you think it's worth trying?
Problems off the top of my head: Crawdads will eat some plant matter. A screen small enough to keep fry out is too small to allow water to diffuse easily. With out a pump stagnation can lead to stratification that prevents nutrients from reaching plants and oxygen from reaching fish. Not all fish will eat plants. The plants you can grow straight in a pond aren't necessarily the best nutrient exporters. An open pond can more easily catch disease. The location where you can put a pond isn't guaranteed to be the location with the best light for growing plants. Ponds spring leaks. It may be difficult to weed. Fish food can be expensive. Regulations for fish in ponds may be different from regulations for fish in tanks. It's more difficult to catch fish from a pond than a tank. They're all going to laugh at you.
Edit: I read pond not tank, so I guess I didn't read carefully. But now Paul's program has pond linked so I'll leave them.
The plants you mentioned have their leaves in the open air, so photosynthesis spills O[sub]2[/sub] into the air not into the tank. Algea may also be a problem. During the day it grows rapidly, and O[sub]2[/sub] spills out from the waters surface (it won't run out of CO[sub]2[/sub] because the water holds more CO[sub]2[/sub] than O[sub]2[/sub] because it forms an equilibrium with carbonic acid carbonate and bicarbonate) then at night the fish and algae together use more O2 than can diffuse into the water.
Thanks, Emerson. Yes, I'd have to be sure to include plenty of oxygenating plants in addition to the useful aquatic plants. I've read duck potato is an oxygenating plant, but maybe from your information it isn't?
I wonder if the fence with holes big enough for fry and baby crawdads to go through would be helpful in allowing babies to escape the adults on the other side of the fence?
I had the pleasure of visiting a rather private aquaponics/aquaculture hybrid in Hawaii a few years back. the owner expressly asked me not to publish photos, but allows me to show them in presentations.
So Ill do my best...
he feeds the system from a 200cfs stream that cuts through his property. He puts about 300k gallons of water a day through the system. his system is about 6 acres total.
It starts with a debris screen, and then flows through a manifold. 10 lines on the manifold feed 10 tanks with 10k gallons each- 20'd tanks. these tanks are topless, just black HDPE pond liner on metal frames. The tanks are aerated, a system run by the water as it hits a small mechanical pump.
Above the tanks are a stand of insectory trees. these provide about 30% of the annual food for the 3k lbs of tilapia raised in each tank.
the rest of the fishies needs are met by dried ground taro and nutritional yeast (NY)
he has a batch grower for the nutritional yeast, though I don't know how much he grows- if I recollect NY is about 15% of the diet of the tilapia, so Id wager hes growing 3 tons annually. Its a big tank, about 6' tall and 8'd.
The yeast is grown using cane and fruit gathered form his food forest margins.
The runoff from the tilapia ponds feeds 6 ac of tarro beds. about 5% of the taro harvest gets ground down into pellets and fed to the fish to meet the rest of their nutrition needs. High in protein, along with yeast and insects, he produces 30k# tilapia annually.
the taro itself is also marketed.
he runs the entire operation on about 12 hours a week. He commented that on retirement from his state job, he would be able to quadruple his current income inside of a year.
the efluent from the loi (taro fields) btw, is cleaner than the water flowing onto his property.
as the gent is a state fisheries biologist, I assume he has the heads up on disease, etc.
three species of endangered island waterfowl call his site home. he grooms the loi using muscovies, and the paths with a Pelibuey sheep, which are short haired and can take tropical climates.
the place is as groomed as a gold course, and he doesnt lift a finger.
as far as integrating this all into a single tank situation, i havent seen it. I suspect that it could be done if one was more interested in john todds living machines than market produce- this guy is marketing, clearly.
Another problem that you run into with a single tank is solids. They will tend to build up if your not filter the water with grow beds or another filtering system. From what i have read many of the water plants that produce oxygen during the day end up taking up lots of it at night.
jbreezy wrote: Another problem that you run into with a single tank is solids. They will tend to build up if your not filter the water with grow beds or another filtering system.
Do bivalves count as a filtering system?
"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men. They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.
I dont know about bivalves. I'm not sure if anyone has tried in a tank based system. The main problem is that the solids will settle if there is not enough turbulence in the system. If the particles aren't suspended in the water then the bivalves wouldnt be able to filter it, that is if they would work at all in a closed system. To keep the solids in the water you need enough fish to mix any solids that hit the bottom. If your tank has corners they will collect solids. If you are interested in aquaponics http://www.backyardaquaponics.com/forum/index.php is a great resource.
any one out there, heard of the french 15th cent monks practices. i,m living in france and thought it might be of interest. they used a combination of agri and aqua culture in a serires of trofs and drains were by the trofs were filled with water by natuarl springs, used with apropiate fish often carp, witch 'most' of witch were eaten at the end of a seasion, then it was drained and used for, cattale or sheep, or left fallow. which in turn fertislied. and so on. what are your thoughts or this practice. and sorry for the spelling im a disleix.... no speel cheek.
There was a guy here in Portland who did a presentation on aquaculture. It was really interesting. He was running a competition with his girlfriend. He grew in the water, she grew in the yard. He was using tilapia, but his conclusion was that in a temperate climate, you should use a temperate fish, like bass, carp, trout? He kicked her ass (in the vegetable competition It worked great. He was also working on an annual basis. End the season , start over in the Spring. I also one dude who tried it and the fish died. I like the first guy's better. John S PDX OR
It saved me from making a potentially fatal error (fatal to to the fish). I was thinking of using a galvanized stock tank for my fish tank, but turns out fish are sensitive to very small amounts of zinc and that eventually the tank would corrode, the zinc coating would get into the water, and the fish would die! So I will be spending about $30 more for a good-quality poly tank.