I recently bought the Fluval Spec for my little Betta buddy. He lives on my desk at work so the Spec was the perfect size for me.
Couple of issues that I found out of the box with using the Spec for a Betta:
Water flow is too strong, the poor little fish would get blown around and the tank needs a heater.
Heater is easily solved. The Marina C10 at Petsmart is a prefect fit in the pump compartment and it keeps the tank right at 78 degrees.
Water flow through me for a loop but ended up being easy in the end.
Even with the water flow turned all the way down it was too strong for a fish with fins of his size. He catches the water flow like a kite.
After trying a few things with no real success I went back to the lfs where I bought the Spec. When I described the problem a solution was presented that they have employed in seahorse tanks.
This simple clamp for $.59.
I had to squeeze the hose a bit to get it on, but once on and tightened down to the flow that I wanted it worked like a charm.