hey.. i have one of my tanks set up with clown loaches in it, and i want to make it rivery, or give them a current area to swim in, i've never set up a tank like this, but i have one tank that has a powerhead and undergravel filter.. is that what people use to get water flowing? my loach tank has ample filtration already and i really don't want to take everything out to change the filter type... anyone know how to do this properly, so the current is pretty strong, but the fish won't get sucked into anything?