My tank also has no filter because I've had alot of fish swim into it and die. My fish do just fine without one and I dont see why some people think you're torturing your fish if you dont have one. Love the plants!
Philodrendon, pothos, and croton are a couple that your frogs would enjoy. Plus they're pretty and it would look natural. I used to have two grey tree frogs that I caught outside and I just went to the woods and got a couple of plants.