another thing you could try would be to make plaster discs to help. You take home depot brand plaster of paris (it doesn't have additives) and mix it thick, spoon into an ice cube tray, let set for a couple of days, then pop out and add to either your filter, or a low flow spot in your tank. You can also add some food to the plaster (low oil/fat or they dissolve quickly) to make it a feeder.