Nick give it a few days it will skim some nasty stuff. My 300 is in 9.5" of water and is working really really well. I like it much better them my SRO. Not that the SRO was bad at all, it was great. This one is just much more stable with the foam head and doesn't seem as temperamental with change. Play with the adjustments over the next couple days to see how it works with different height inside the skimmer.