Hey Alexandra,
I fish tank works just fine. I have one for my Grey Tree Frogs and one for my Fowler's Toads and all are doing great. If you don't need high humidity a screen top gives plenty of ventilation for the critters. I have pic of both habitats in my albums if you want to check them out. Just make sure you clean and rinse them thoroughly. Also it's good practice to have the tank set up and ready to go before you move the critters into it. I had mine going and growing for a month before the critters moved in.