Pale areas appearing on chalices

[The Escaped Ape]

I bought some chalices last week, but on one of them, a couple of small areas of pale/whitish tissue have appeared. The other also seems to have one area forming.

They're both on the bottom of the tank (18" deep), out of the direct light from a 150W MH with a Radium bulb (as in the rock work is between the bulb and the coral), plus 4 T5s (pure actinic x2 and actinic plus x 2).

Thoughts I've had include possibly low magnesium, as I've heard this is a must for chalices, problems with my alk (will test tomorrow) or possibly being picked at by my African Flameback (I've seen him nip at them, but it seems to be half-hearted and not really cause any damage).

I'm planning to order a pH monitor from the States to keep an eye on my alk, plus a mag test kit and supplement (it's so expensive here, it makes sense to order it from the US). I'm also likely to change my salt soon, to Coral Reef Pro from Instant Ocean, as I understand IO is low in magnesium and CRP seems high in both calcium and magnesium.

Anyone got any theories?

 

[pciscott]

Lack of light, too much light, or a nipping fish can all cause chalice to loose color. What are your phosphates and Nitrate and do you have a lite bioload? If your water is ultra low in nutrients your LPS can starve and loose color as well. When you see a fish nip at LPS, he is doing it more when you are not looking in my experience and I have had no luck with angels in my mixed reef. I had a similar issue with some of my chalice coral when I first started running biopellets, my water got too clean too fast and my corals stressed, my fix was adding several more fish and feeding more often and my tank looks better than ever. Some people spot feed LPS coral, the corals respond well, but if a fish finds an easy meal you are teaching him to eat your coral. I had too pull a bristletooth tang out who destroyed several colonies. I do not spot feed anymore and my colors are great. Good luck with your problem, Loosing coral is no fun and I have been there. I would start by catching the angel.

 

[The Escaped Ape]

Thanks for the advice Scott. I've been keeping a pretty close eye on the Angel and he's not an inveterate nipper yet. But you're right, I might have to get rid of him.

The nutrient level is not ultra-low, despite having just recently moved to bare bottom. I'm still getting algae on the rocks and glass - actually more than I'd like, possibly due to a combination of having just changed over and feeding 2-3 times a day since I got a Fathead Anthias and a couple of very young fish that I assumed needed feeding more than once a day. I need to break out the test kit and do some all round testing.

Actually, I'm wondering whether to get rid of the GFO and GAC reactors I'm running. They are a pain to change the media on and I'm not sure if they're necessary when I'm running bare bottom.