I know this is a few weeks old and you've probably already set your new tank up, but I don't think you really need a filter for clawed frogs. They do produce a lot of waste, but frequent water changes will keep this down. I have several and have never used a filter, and they are all perfectly happy and healthy. In fact, constant water movement (like the kind that a filter would make) can stress them out because they are from shallow, stagnant ponds.