I contemplated getting the tunze nano DOC skimmer. I heard alot of good reviews, and one bad one. I think the problem with small skimmers is that an important part of skimming is contact time, and a small sized chamber makes this impossible. Compared to what a decent sized skimmer will pull, nano skimmers are crap IME. I think you are better off just putting an ASM or Euroreef (something with at least a 5" chamber) in your 10 g sump.