the bottom of the tank is 8', the top is closer to 6', it holds about 700 gallons..i base my fish load on the amount of filtration i have... i'll be adding to the filtration this year (following cecil's threads closely!) and should be able to bump my stock up to around 200 fish safely.
i've got my airpump hooked up to a UPS battery in case the lights go out.. still working on beefing up the batteries..
tilapia need warm water.. i was lucky to get mine through the winter, the water got into the 40's.. only lost 3 or 4..before i started a heater up in the basement.
i like that the yp and bg keep the tilpia in check... i can set up a breeder tank for more tilapia if needed..and the crayfish i'm using have been multiplying (i would say breeding, but marmokrebs don't breed.. they are parthenogenetic) like crazy.. i've put 40 or so larger crays into the pool (as well as a couple hundred small ones that got eaten pretty quickly)
regarding nutrition.. what you get out of an ap system will entirely depend on what you put into it (nutrient wise) - i have noticed that my farm raised perch seem to be a little bit "fattier", but taste delish