HELP! Zoo's Dieing

[mjsdas]

Almost all of my zoanthids have begun dieing in my tank, and i cannot seem find the cause. It started about 2 weeks ago with the polyps closing on one of my colonies. since then, all of my zoanthid, near a dozen or so, colonies are closed up or are startin to close up and not open anymore. The ones that closed first have deteriated to where thet are starting to break down. Nothing else in the tank (LPS and Sofites) are showing any signs of death or anything like the zoanthids are. If you have any idea what is causing this, i would appreciate a speedy response. Any type of trouble shooting tips to help me find the problem would also be very welcome.
So far i have checked my water levels, replaced the carbon in my cartrage filter, and done a 20% water change. (I dont a 10% change weekly)
Water Levels: Ammonia: 0, Nitrite: 0, Nitrate: 0, Phosphate: 0, Alkalinity: 6.2dkh, Calcium: 400, PH: 8.2, Specific Gravity: 1.024
I hope i someone can help me because not only do i have quite a bit of money sunk into these colonies, but the zoanthids are my favorite corals and i would hate to lost them all.

 

[reef-addict]

:notsure: How is your water flow in your tank vs where the zooanthids are placed? Are they in low flow spots or heavy current?

 

[dusty]

do you see any little round snails close to the polyps? I am having the same problem and I think that is the cause

 

[jourdy]

hmm.. zoanthids, in my opinion, are one of the hardiest corals available. i never had trouble with mine..
how about trying a freshwater dip? it takes out all the pests in the colonies.

 

[mjsdas]

No snails, no cheese, but i think i figured out the problem this morning...i decided to recalibrate my refractometer and it turns out that the salt was way way to high. I kinda assumed that u only had to calibrate it once and then it was fine, but from now on i'll do it more often. Hopefully the colonies will come back now.