Just about ready to throw in the towel grrr

[sphelps]

Originally Posted by digital-audiophile

I have been very strict about my dosing regiment and change 5% water weekly with RBS (zeo guide recommends 10% with other salts)

I am running a euro reef rs135, it is a decent skimmer allthough I wish I had a bubble king, but for the price this skimmer works well.

Personally I think your skimmer is your problem, I really don't think a ER 135 is big enough for a 90 gallon + sump system when using Zeovit. Although it may be a good skimmer for the price it just simply will not do what you're expecting it to. Basically you're flooding your tank with bacteria and bacteria food to eliminate nutrients but there are harmful byproducts that need to be skimmed out. It seems fairly obvious to me that skimming has not been effective and these byproducts along with excess bacteria and b-food has resulting in a cyano outbreak.

Although the guide does state that 5% weekly is fine when using RBS it also states this would be for the purpose of only replacing elements. In your case you should change more water to help remove byproducts and excess bacteria and nutrients not removed by your skimmer.