NO! unless it is all local incoming animals, the species wont mix, and will screw eachother up. I am not sure if it is true, but I have heard fish waste kills frogs REALLY easily. Since you are a "rescue" you will be having lots of injured animals come in... Please, every "I'm gonna start a rescue" post goes DOWN badly. I think the last person who started one got such a bad response, and by defending themselves, they got banned. I jsut re-read you post, and you say a different pond for each species... That might be a little hard to do. How bigs you're yard? This will cost almost all of your money, almost all of your time (not free time, but TIME) and be very stressful...
keeping a few pondfuls of stuff IS a good idea, however. that would be MUCH cheaper and easier than a rescue service in the long run. With rescues, expect turtles that need expensive vet service, and some moron who comes to dump off an alligator, a bunch of half dead frogs that you will have to nurse back to health... Then when you put them back in the wild, you can SCREW up te ecosystem badly (unless, of course, everything is local, but it is illegal to keep wildlife captive without permits).
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