Which Fish?

[Duck and Dive]

Guppies! They are easy to keep. Be warned they breed a lot if you mix males with females. If you dont want any fry only have males (males are more colourful) and you can keep platys with them.

 

[Matty P]

You might want to add a couple more air stones/pumps to help oxygenate the water more. (I know you already have one)