I am using 55 gallon barrels because they are very cheap (often free) in my area. It is really important to find containers used for food products, NEVER chemicals, which could eventually leach back into the system. Another option could be to build shallow pools with a layer or two of cinder blocks and concrete. I have added some examples below and a short video on building a cement Koi pond.
The system is designed around two main areas: the GROWBED and the FISH TANK. The sump, as a third part, works to minimize the amount of water being drained from the fishtank each cycle. Maintain a 1:1 ratio a the start, although a 1:2 ratio (fish to growbed) will work. This will increase the amount of growarea but a sump will be needed. Don’t want to leave the fishies flopping around in a puddle.
I believe that for my Rwandan friends, a concrete pool would make quite a bit of sense as well. What about building two pools similar to this style. They could be sized differently though, with a divider in the fish tank to act as a sump tank. The pump could circulate to the growbeds from the tank while the sump could maintain a steady water height.
How big? Well… 7.5 gallons of water will work for a cubic foot of grow area. Assume the growbed will have a depth of one foot. A 50 gallon tank will support a 7 cubic foot bed. What about Metric? Well, the ratio is a 1000 liters to every cubic meter. You can push this later by adding more grow areas. I am keeping the 1:1 ratio right now than will add dutch buckets as the system stabilizes. My way of looking at all these weird numbers is to picture a fish pond/tank in one foot sections, than adding the sections to decide on the grow area. A 4′ by 4′ pond, three feet deep would yield 3* 4 by 4 growbeds. Let me know if that doesn’t make sense 🙂