Zoa disappearing

[phenom5]

I recently added 10 zoa frags. It's been about a month, and 2 of the frags are gone, all the polyps just melted away. 2 more of them are doing better, but seem to be slowly losing polyps. The rest are doing fine. An old zoa colony that i've had for a long time is doing okay, but it has lost some polyps also.

My water...
NH4-0
NO2-0
NO3-very low
Ca-400-420
ALK-~10
pH-8.3
SG-1.025
Temp-79-81

I do regular weekly water changes of 4g, total system volume is 22.5g.

There are only 2 things that I can think of. One, as it got colder, the temp on my tank dropped for a few days. It was 72-74 when I caught it, added a second heater, and slowly brought the temp back up, and now it's stable. The only other thing I can think of is my light. I need a new HQI bulb...badly. I'm way past due, and have it on the things to buy list, just haven't gotten it yet.

I've done lots of after dark, flashlight viewing, and as far as I can tell, there are no predatory hitchhikers that are eating my zoas. All zoa frags get a 5 min FW/ Lugols dip before the go into my system.

Any thoughts? Could it be my light? Or do you think that it's something with the temp?

Thanks :thumbsup:

 

[FishAreFriends2]

I'm having the same issue, I had a nice coloney slowly shrink and bleach at the sametime. I have no idea whats going on.

 

[Pufferpunk]

See: http://www.reefcentral.com/forums/showthread.php?s=&threadid=1252294

 

[phenom5]

Thanks for the link Pufferpunk. I think I'm going to head to the drug store after I get off work later today.

Quick question, something that I probably could have asked in your thread, but...

any recommendations on brands of vitamin C? What exactly am I looking for? I assume, based on what I read, I'm looking for something that is pure vitamin C (or as close to it as possible).