Skimmers?

[The cats wrasse]

Just a guesstimate for how many protien skimmers are sold per year?

 

[Sailfin11]

A lot. I don't really know a number, but I think most people buy one skimmer for their new tank and use it until they take the tank down, so its not like heaters or pumps that we change out frequently. Retailers and manufacturers are probably the only people that could give you a true answer.