http://www.drsfostersmith.com/Produc...1&N=2004&Nty=1
I use these on my 2.5 gallon and it has flow controls also. I keep one in each. They do fine.
I made a lid out of plexiglass also, I made it so my cord for the 25 watt heater and for the filter would have access.
Currently I have a betta in each of my tanks (2 tanks) and a 3rd 2,5 just growing java moss.