The NanoSkim 40 Protein Skimmer is a superb hang-on skimmer from Aqua One, suitable for aquariums up to 40 litres. Don’t be fooled by the NanoSkim 40 Protein Skimmer’s size, this is a very capable protein skimmer, ideal for use on smaller aquariums that don’t have a sump and where space is at a premium.