question about zoa health

[cngh]

i have zoas mounted to a large rock in my tank that *for the most part* look healthy. it's grown from about a 1x1 frag to cover the rock in about a 6 or 7 inch diameter spread.

occasionally tho, some sections (not always the same sections) seem to wither back and it looks like the zoas are choking and are closed and look like little nubs. it'll look that way for a couple days, then over a few more days it kinda looks like they're shedding skin but then they'll get back to normal and look totally healthy and fine.

what causes this? i've noticed that it's spreading to separate colonies so i'm guessing it's a fungus or bacteria or something (but not nudis or pox - i'm almost positive of that). the rocks are too big to dip and moving them would totally disrupt the rock scape.

params are:
SG: 1.025
CA: 400
dKH: 7-8
Mg: not sure (last i checked a month or so ago it was at 1250ish)
Amm: 0
NO2: 0
NO3: 5
Phos: .5

i use ro/di for topoff, and DDH20 for my salt mix. i dose vitamin C (a few drops of brightwells per day).

any ideas what causes that and how i can address it? thanks!

[waterman78]

Try dosing iodine...this may help heal the coral. Just my two cents!!!

[cngh]

i occasionally dose iodide (not iodine)- the brightwells version. i only dose a few ml's btwn WCs, but i haven't noticed any correlation; it seems that the zoas decide to look all tore up whenever they want to. i think my dKh is a little low too, so i've been slowly trying to raise that up as well... i hope that's what the reason is and that once it's up to around 9-10 they'll be happier.

[mathdoc]

it is just something they do. If you scuba dive, you can see it even happens under natural condition in the oceans.
That is why I think zoas can be both the easiest and the hardest things to keep in your tank.
I used to dip them and try to help when it happened, now I just wait and hope they will be OK in a week or so.

[shapermike]

I does Vit c when I am having problems and watch your fish, some times they nip at the allege and irritate the zoas