they really arent that great, most of the gunk just gets trapped which just leads to problems.... high nitrates, rotten egg smell, etc. so I would just stick to gravel vacing.
If you are tired of doing gravel vacs you might want to consider switching to sand, I did. The waste and such just sits on top so you just have to hover over it with the gravel vac and it will suck it up so its a lot less work.