I have a unicorn tang, a regal blue tang, percula clown, lyretail anthias, mandarin goby. I have a Marineland pro series light with a 150 watt 20k halide and 4 39 watt actinics. I just changed my bulbs, but the thinning out started happening before I did that, so I don't think I'm burning them. Besides, I've had my zoas for about 2 years. I added a hammer coral about 4 months ago, but other than that, nothing else new. I was told by my LFS
that some hermit crabs do pick zoas off the rocks. What types of diseases are you talking about, Scarothelia?