It's good to put your powerhead on the opposite side as your water return valve so you can try and reach different areas of the tanks. The point is to get rid of dead spots where water isn't circulating like behind rocks and such
Also, to get those suckers out, when you get close to finishing your cycle, put there food in some kind of container or even the net to feed them. They'll get used to having to go in and when you're ready to take them out....ZOOP!!! Scoop them up!!!! It may take a few days worth of feedings to get all of them out, but it's better than having to move stuff around and deal with a dust cloud!!