Unless you have an outdoor pond, I would not buy 28 tads. When they mature into actual frogs there is not going to be room for 28 froglets in there, let alone like..two..maybe. Thats just while theyre little. When they get bigger I would keep it down to like one frog per 10 gallon if that's all you've got. But, really, bullfrogs need lots of swimming space, and they get so big. An easy way to make a large enough aquarium for a bullfrog for cheap is a large tupperware storage bin. They run about 10 bucks for like a 40 gallon one and then all you need is your filter, pump, and rocks and logs and such. Easy peasy.