How big is that and how many do you have in there? I had a 20 gallon tank for my tadpoles and I was doing DAILY water changes with it. They literally do nothing but eat and poop. They look like they could be tree frogs, but I have come to the realization that tadpoles are near impossible to ID. My grey tree frog tadpoles looked very similar to my leopard frog tadpoles, but the leopard frogs ended up being about twice the size of the grey tree frog tadpoles before popping legs. Here is an ID table so you can see if that helps you out a bit - https://s-media-cache-ak0.pinimg.com...e14d8ace48.jpg

Here is my tadpole diary if you want to take a look through it - http://www.frogforum.net/showthread.php?t=36240

Seriously, have fun with these guys. Raising tadpoles was a blast!