boattos,
I am currently housing one of my male VT bettas in a 5g. I have a Tetra whisper filter and no heater. Personally I don't think current is that big a deal, but I think it is important that there is a place in the tank where they can get out of it. My betta loves to swim in the current, and when he wants out of it he knows where to go. Also I don't use a heater and my tank stays at a constant 73 degrees. Its all personal opinion, as long as you keep your fish happy then thats all that matters!
Justin