Best HOB protein skimmer

[ReefBeta]

Nope, I’m thinking of reactors. With lights right on them, don’t they grow algae on the inside acrylic?

You mean the acrylic will get dirty like the tank glass did? In theory it will. But in my experience it's not that much in practice, probably because it's too close to the light that the par is too high for even nuisance algae to handle. Also when harvesting chaeto, I'll just brush the chamber as well. It will stay clean enough between harvesting.