In the sump is housed the real heart of the whole system: a Bubble King 300 internal skimmer that is an expensive piece of equipment but worth the money. Without that skimmer I believe that it would not be possible to keep all the fish that I have and keep my corals with acceptable colours. In the past, I have connected the venturi to a 300mg/hour adjustable ozonizer that I dosed at roughly 150 mg/hour for 8 hours at night. Recently, I haven’t used it and it appears that I do not need it anymore.