If you really want to see some magic, set up a fish tank of about 40 gallons in size (smaller tanks will work but won't yield much...). Add in gravel about the size of baby lima beans or a little bigger and layer it about 3 to 4 inches deep. Add a fish called "Tilapia" in there, maybe a few, and take care of them until they get big enough to eat.
The feces from this fish is about as potent a fertilizer as one could ask for. Siphon off the water from within the gravel, and it will come off nearly black from all of the droppings in there. If you have a large garden, you can used this water directly. If you have a small garden or just a few potted plants, then wait until the water in the bucket has settled and remove the clean water off the top until you only have a few inches of the really rich stuff at the bottom. The first time I tried this I had the whole family sick of zuchinni that season! The fish is recycleable, too. Tilapias are one of the fastest growing and easy to care for freshwater fish that inside of a few months of good care is big enough for the table (and *quite* delicious, too). Our friends in Florida could probably tell you all about the hardiness, growth rate, and reproductive capacities of the tilapia since it has almost wiped out native gamefish species there.
I'd posted an idea for ROOFTOP GARDENS or vacant lot gardens, these were many small gardening beds planted with vegetables and small bushes, made out of Children's round plastic pools, the hard kind. Not the blow up kind. A gardening pal read it and tipped me that many years ago the govt. posted some plans (in one of those gov pamphlets, no internet then! ) for making a kiddie pool fish pond capable of raising trout, tilapia and it was THREE POOLS put together. She said "I've hunted for those plans for many years. Basically it's a tri-level pool like a waterfall, or like those fountains people make with a small motorized pump and the water flows from the bottom to the top where the dirty water is trapped on rocks; the second level had rocks too that the clean water flowed over back into the bottom pool which had the fish. Since it was moving water trout would grow in it. Nice fresh trout. But Tilapia would love it. I can't remember all the details but the dirty water was cleaned by flowing over the rocks. I would think there would have to be another pump to get the fish fertilizer out of the system and then the human carries it over to the compost pile. I have remembered those plans for 30 years now and have probably forgotten a few important details; however, it was kiddie pools being utilized.
Ya think we're on to something? INVENTIONS MAKE MONEY!
http://survivalplus.com/foods/page0006.htm
has a geodesic fish farm