I have a theory that it's all about the nitrification and the production of Nitrate. Nitrates make your plants thrive so let's make an abundance of it.
Your fish will love you for creating a pollution free tank for them to grow in, but it takes fish food and waste to bump the Nitrates up. If the water remains clean the plant roots and your fish will be happy to eat all you can feed them. Grow them out big and push the Nitrates!
Throughout the process I kept coming back to the basic above ground pool as a combination fish tank / grow bed / bio filter. It's big and cheap, and the cost of pumping will be reduced if the nutrients are allowed to circulate below the surface rather than vertically.
Solids extraction always seems to be a hangup with this idea.
So far I've only come up with two options - Scuds or a pool vacuum.
My best ideas for pure water seem to center around Moving Bed Filters. The main advantage is a smaller filter which will hopefully require a less powerful pump
Next problem is how to keep the roots safe from the fish?
So far Wicking Pots or a standard net pot raft with a screen attached to the bottom of the raft have been my best options.
James Troyer suggested to me that I could sew a basket from weed cloth and hang it in the water from PVC buoys. This Wicking Basket would remain moist and the basket could be filled with compost to further enhance the grow media
Does any of this sound like the right direction? This has become an obsession and is causing me to neglect my daily responsibilities. But I keep thinking I'm getting so close. I often find myself justifying just one more experiment or research one more idea. I'm finding it difficult to let go of this as I feel this is getting very close to the ultimate backyard system.
My experiments with Airlift Pumps have been marginal and trying. At this point I'm ready to go with an impeller pump.I believe the airlift pump requires more depth than the shallow depth of the pool allows.
Air stones would also be placed along the edge of the pool to further aerate the water where the fish would have full range of the pool.
The plants would be suspended on rafts which hold the media filled fabric 'Smart Pots' at the surface allowing them to wick water.
Total power used would be 1 - 50W 70 lpm air pump.
1 - 240W solar panel with battery storage and a 400W inverter would supply power 24/7.
Test results for a raft idea:
I filled a 10" pot with wet pumice.
The filled pot weighed 6Kg.
An 8" pot weighed 2.5Kg
6Kg should displace 600000 cubic mm.
I then floated the pot on a piece of foam insulation 1105mm X 457mm = 50490 sq mm.
As calculated about 11.9 mm was displaced.
|Two pieces of 1-1/2" insulation bend a little but this confirms the displacement.|
I calculated that a piece of foam about 15"x15" would displace about 1-1/2" for a 10" Smart Pot filled with wet pumice. The raft could be covered with a wicking cloth or a hole could be made for the pot to set into and make contact with the water. I imagine a few large rafts with several pots on each would be best to maintain stability and avoid tipping over.
One issue that may need to be addressed is solid waste removal. I'm open to suggestions.
Possibly a pool vacuum would work.
1 - Above ground pool. (Seasonally inexpensive in the fall.) $200.00
1 - 70 Air pump $70.00
1 - Perforated container (IBC) $90.00
3 yards of media (Price varies) $200.00
Rafts (2 sheets foam insulation? ) $70.00
Smart Pots $150.00