Hi, I have just set up a 28l tank for my 3 African Dwarf frogs. At the moment I'm running a Rena Filstar 100 in there but it's the one I normally keep as an emergency spare as it doesn't stick to the glass for long! I'm looking for advice on a small internal with an adjustable flow rate as the frogs need as little current as I can manage. I originally thought of a sponge filter but there would be too much surface movement and the vibrations from the air pump wouldn't suit them. Any ideas? I'm not used to researching internals, all my others are external so I'm on kind of new ground here!