Aquaponics on a fish farm

[Vincent Seah]

Hi,

I'm currently testing a floating platform which I built on an existing fish farm as an experiment. However, the results have not been good, am hoping to get some advice here.

Here are the details:
Size of platform: 2 meter sq (less than 1% of the entire coverage)
Plants used: Mint, basil, dill, red cabbage and various ornamental flowers
pH level: varies between 6-8 depending on time of day
Ammonia level: minimal
Nitrate level: minimal
Types of fish: Ain't sure about this but the owner did assure us that there are a variety of fishes in it
Temperature: 28-32 degrees Celsius
Growing media: soil
Climate: Tropical throughout the year

Symptoms:
Yellowish leaves
Slow growth
Stunted growth

Have been testing this for 3 months but can't seem to figure out the problem.

Please note that the fish pond is in an open area and there are subjected to every environmental conditions.

[TCLynx]

I think pond aquaponics could be made to work, however it will have very different complexities from a normal recirculating tank type aquaponics. 

Remember it is all about letting the ecosystem balance.  If a pond is already in balance with it's proper amount of algae and other things, then simply adding a raft of plants doesn't work well since they need a different balance of oxygen and nutrients and if the system is already in balance, there isn't enough of those things left over for aquaponic production.

[Vincent Seah]

Thanks for the replies, the problem is indeed a roots rot issue due to lack of oxygen. After investigating further, I realized that there is an increase in the algae build up on the net underneath the board, which is limiting the water/air flower to the roots.

Have changed the net since, and the new net has a bigger hole so as similar issue won't happen again. Will post up the pictures soon

Actually, I strongly believe in the benefits of a pond aquaponics system and do think it should work. However, I do agree that it is much more complex than a traditional system. Well, I guess my trial will have to continue.

[Jon Parr]

I've got an idea for improving your pond system. How about taking a 10' length of flexible drainage pipe, and securing on end to the middle of the underside of your raft, and a weight on the other end to hang it in the water column or rest it on the pond floor. Into the pipe you could run an airstone and a deep water air pump, as deep as possible for your pump/power options. The ascending bubble stream will oxygenate a huge flow of nutrient rich water off of the pond floor up to the bottom of the raft, and provide some current to the roots as well. If my recent studies are true, then the anaerobic floor of a pond is rich in nutrients including iron. 

[Jon Parr]

Btw, if your pond is off-grid, then a small solar grid would supply the air during the days, which I assume would be enough. My deep-water tetra air pump will push water 8' down, and runs on 7.8 watts. Harbor freight has 5 watt solar panels for $20, so get 2. I think I'll try it on my little pond. The circulation will probably improve the pond health as well.