I agree Caryl gives good advice.
The u/g filters are good Aqua and as said previously they do not need a lot of maintanance (nil). suits me fine
When I requested one for the hexagon tank the sales person tried to sell me a small one telling me it was the only hexagon one made. WRONG
I went to another pet store and WAHOOO there was the one I wanted, larger, almost twice as big and it fits great. :lol: