My 20 gallon tank's residents are 1 male platy and 2 females, 1 female betta, a nerite snail and 4 julii cory catfish. Any fish that I could add safely? I would prefer some that will eat algae on plants, but it's not a necessity if there are none I could fit in my tank. I might upgrade it in 1-3 years, so i would be open to buying a small fish that grows slowly into a big fish. EDIT: Forgot to add that my PH is 7.2 and no ammonia or nitrite. I do 40% water changes every week.