Growing Power’s AP System Design is soil-based…
“We fill our growing pots with a mixture of coir and compost. The coir is made from discarded coconut husks and helps wick water to the plant’s root system. The compost provides extra nutrient to grow an abundance of crops within the system. Traditional hydroponic growing, or growing without soil, relies on fish waste alone to fertilize the crops. The problem is, you can only grow crops with lower nutritional needs such as basil. For example, in most traditional hydroponic systems, Boron is found in very low quantities. Boron is essential for flower development in crops – tomatoes, peppers, and cucumbers – which means that production for these kinds of crops is very low in hydroponic systems. At Growing Power, we solved this problem by adding nutrient rich compost to the pots in our system.”
- To safely use chlorinated water, use ‘dechlor’ which is sodium thiosulfate.
- Acceptable range of ammonia — from gills for tilapia — is 0-30 mg/l and nitrate = 0-25 mg/l
- To start up the system, start with ‘sacrificial fish’. Do not use bait fish or import from the wild. Maybe not healthy, could be diseased.
- It’s hard to starve a fish to death. If you don’t feed them they just don’t grow as fast. Quoting: (“At Growing Power, we feed our fish duckweed, ground-up salad greens from the greenhouse, worms, and Tilapia love to eat algae from the side of the tank.”)
- Stocking density: One 3″ fish/gallon. Max 80 fish per 100 gallons. There is 3X times that volume in the total circulation, between sand filter and grow beds.
- Growing Power uses a ‘soil-based’ system. (See quote above). They put pots filled with wicking media in the grow bed trays flooded with water from the fish tank.
- Don’t germinate the plants in the system. it’s a ‘grow-out’ system only. Plan for rotation to keep balance between plants and fish. (On planting cuttings vs seed: note that cuttings will flower at the same time as the parent plant.)
- AP systems want to run acid because of fish respiration. CO2 -> carbonic acid.
- Automation is nice, but need hands-on. (There are many things the automated system can’t catch — like a squirrel swimming in the tank that so freaked out the fish that they didn’t eat for 3 days…)
AP Tank design workshop notes:
- Use carriage bolts, not screws. Install with round head on inside so doesn’t rip liner. Liner is 45 Mil EPDM. Do not use type sold for roofing. Fireproof coating is toxic.
- System filled with water weighs a lot. Must be very well supported and totally level (concrete floor?)
- 4×4 pressure treated posts, predrilled. looks like 2×8 joists at 12″ O.C. under 1/2″ plywood floor. sides are 2×12’s
- Installing liner: prefold at chalklines. Put water in tank to hold in place. Use styrofoam as anti-abrasion. Leave everything loose, and push liner into corners. otherwise will stretch & tear when filled.
- Use bathtub drain without strainer. mark location on liner. With utility knife cut ‘pie slices’ in EPDM, centered on drain. Do not use silicon. it is toxic.
- Prefer submersible to in-line. Use 1-1/2″ PVC. Use elec conduit male/female adapters for bulkhead fittings. Cannot use tapered thread npt.
- Sand filter is a ‘safety’. Ramp up slowly.