Hey, I have lots of experience with keeping fish - tropical, native and ornamental frshwater. I have worked for over 3 years at an aquatic retailer where I care for and sell extensive ranges of tropical, brackish and fresh water fish. I also help people create, set up and maintain tank systems and ponds of all sizes so if you have any questions just ask!! I personally have a huge tank in my living room containing all sorts of native fish inc. bream, rudd, tench, chub, minnow, gudgeon, and stickleback. I also have a community tropical tank and several ponds with all sorts of coldwater fish and terrapins in!
Nathan is right especially if its one of the xenopus toads (usually albino)! If it is one of the smaller dwarf clawed frogs however you should be ok as they rarely grow over 2 inches and are therefore only a threat to the smallest of fish or fry!