Alright, 41 pages later...
Im going to try and hit all your questions then make some suggestions.
Preformed ponds- Home Depot, Menards, Lowes, ect. Check in Fall, Menards all pond stuff is 40% off as soon as summer is over.
Canisters- Same as above, I got my sunterra 2000gph canister and 3000gph internal (in the pond) pump for less than $130. Works great, never even opened the canister in 10 months, pump has run constantly, no problems what so ever. Flow is great, Caimans (esp Cuviers) are often found in "faster" currents.
Humidity- Def need exhaust fan, I wouldnt worry about heat or humidity loss as long as water is heated and basking spots are available. Just puton a timer or something and monitor.
Turtles- Fine as long as they are large enough to not be considered a food source. Snappers = Missing toes on the caiman, stay clear.
Fish- Bigger is not better, they will be struck at and they will get fd up. Smaller seems to be not worth the effort especially if the caiman is well fed. Id just go native and throw some bluegills in for a snack (hell get them eventually but not right away, there is one in mine thats been there a couple of months now). Pointless anyways as you wont be able to see the except from top. If you want to chance it then know that my 2 footer has eaten larger bodied fish at about 8". Pop the head off, swallow, whered the body fly? find, eat.
Moving- I use a clear rubbermaid box, put it over him then slide the lid under, done. Dont worry about him chasing after you when you enter his cage, he will hide and only strike if you corner him, if even then.
Lighting- Everywhere Ive read says no special uv's are needed. Still not a bad idea especially next to a basking area.
Food- Try and stay away from goldfish feeders. Same reasons as for fish. Love crayfish (any crustacians), there is a type that is non territorial and asexual reproducers, cant remember which. I breed mice also (1.5 seems to produce plenty for my one). Whole body prey as they get significant amounts of calcium from bone. Occasionally I'll give chicken breast or some beef that Im about to cook for myself. I see you have some rabbits and hamsters? I think. Baby bunnies prob ideal bc they cant digest the hair (prob provides their fiber though). Not sure if youll like that idea or not. Can also be plate trained with prekilled. Reduces aggressiveness, tendency to associate hands with food. Also takes the fun out of having a predator IMO.
Substrate- I use sand for many reasons. They almost always deficate on land same as owning a cat, get to scooping, 2 mins later your done. Also sand sinks to the bottom of your ponds and sifts through regular aquarium nets. If you use wood chips or soil youll be pulling it out of the ponds too much, and youll never get all the soil out, it sifts through the nets too. Wood chips would be fine just plant grass types around edges of ponds so most comes off before he/she enters the water.
I think thats it, if you have anymore pm me.
Personally I think your enclosure is plenty big for two+ of any species of caiman, plus youll have breeding potential. Only problem is swimming area, ponds are a little small, but I see you working on that already. Idea... Instead of taking out the smaller one just add another, 3 ponds and less work. No need for depth, 1' of water is plenty. Mine is only about 150g but is 6ftx4 1/2ft kidney bean shape= less depth more swimming area.
