Paul,

I have two moors in a 10 gallon. When they get bigger, I will
upgrade them to a 20gallon (or more).

Can I suggest you get an ammonia, nitrite and nitrate test kit.
Change at least 25% of the water weekly. If you're fish still
look ill, increase the frequency of the water changes.
Don't over feed your fish either.

Stick an airstone into the tank too. Ensure you dechlorinate
your water before water changes too.