I'm not sure if this is a question better suited for the equipment forum or the substrate forum. Or even the plant forum. But anyway here goes. I went to the LFS today for sand for my in-progress 29g planted tank. I got some advice from the employee at checkout to look into a powerhead for my setup with sand, because he predicted my filter would eventually choke on the sand. I told him the filter wasn't going be on while I put in the sand (no fish in the tank yet). In fact, I was just going to let it all settle for a few days before I even turned on the filter. He didn't have much of a response to that, except to say that eventually sand will kill the filter impeller and that I should consider getting a powerhead (instead?). Here's what I think he was trying to tell me: a filter will - suck up water too close to the sandbed and eventually choke on the sand (i.e. impeller will give) - increase ammonia levels in the tank because the ammonia gets "stuck" in the filter a powerhead will help because - the ammonia will not be "stuck" in a filter - the increased flow will somehow help with the sand So...I take advice from the LFS employees with a grain of salt. I came home and read up a little on powerheads. My understanding is that they can act as the motor for an underground filter, or generally just create flow and surface agitation, which increases the oxygen content in the tank. It also approximates faster-moving waters for fish that are from such areas. I still don't understand the rest of what he said. I don't understand how ammonia would get "stuck" in the filter, and I'm not sure what he was saying about filters and powerheads together or individually. Forgetting about the fish for a moment, what would a powerhead do to help a sand-substrate setup? Would a powerhead either in lieu of or in conjunction with a filter make my tank stock happier? I'm planning so far to keep cory cats (hence the sand), a pair of German Blue Rams, and some schooling fish (quite possibly rummy nose tetras). I was considering putting in a dwarf gourami as well, but still undecided as it's a long ways off. My first instinct is that a gourami would be disturbed by a powerhead though.