Reef crystals,but I only do 5% weekly change.That is part of the reason I am thinking of doing the Neo Zeo system,seems a little cheaper as I am on a budget and running out of cash for my Aquarium addiction.My understanding is being on one of these systems will allow you to do smaller water changes.
Reef Crystals should not be used with any probiotic systems, the alk is too high. NeoZeo isn't any cheaper than ZEOvit, you dose a heck of a lot more of the product with NeoZeo than with ZEOvit. I was experimenting with NeoZeo, for about 4 months. I'll likely stick with ZEO...
