My experience with Vit C & Zoas

[Superlightman]

Zoas and palys need stable nutrient levels and do best with nitrate levels a tad elevated; between 5-10. You also need to keep phosphate no lower than .03. Yes, they do like water on the dirtier side, but still within the range that even finicky SPS corals are happy with.

Most reefers having problems with zoas let either nitrate or phosphate bottom out correcting other issues like nuisance algaes. This can't happen. Smaller zoas in particular can't handle nitrate dives, and a 10 point dive in nitrate when your zoas are used to a higher level can cause them to receed and look bad. While zoas are regarded as a beginner coral ironically aren't suitable for newer tank nutrient swings. Newer tank owners often find themselves in a dilema of having too much nuisance algae growth while having an investment in soft corals that don't like the inevitable nutrient dives and aggressive water changes that are a result.

Also, the smaller the zoa the more sensitive they are. Larger zoas like gobstoppers for example can take a lot of abuse, but hornets in particular get a rep for melting, and it's mostly due to nutrient swings,

Actually they are my biger zoas that curiously suffering,the smaller seems to be well,i recently made my phosphate and nitrate drop,but they are still in a high range around 10-15 for the nitrate and 0,14 for the phosphate.

 

[Superlightman]

Could it be that they not like the zeolite also?