Thanks for that advice. I will only have two tads. The water area is 7 1/2 gallons and 6 in deep.It also is planted with 5 live plants for both cleaning and aesthetic purposes. I am also keeping in mind the amount of food being fed that may not be consumed. With an established natural bio-filter,an air pump, and only two tads how often should I do a partial water change? Also how much water should I change? 20%? 25%? 50%? Thanks to everyone who has posted advice and who will take the time to advise me on this project. My son and I are enjoying learning more about this and looking forward to our spring tads and a possible new frog "pet".