Blasto colony dieing. Why?

[Ocean Lotion]

I have a colony of Blasto Wellsi (?) That is dieing. The polyps are receeding and then the bone white base becomes exposed. It has been slowly doing this for months. I have 3 other Blasto colonies that are doing great. I have been spot feeding reef roids and reef frenzy but it is like it has stn. My water parameters are textbook except my nite ates are are 40 right now. Though Blastos were almost bullet proof. Any ideas why they may be doing this? They did undergo a couple lighting changes as I downsized from a 75 to a 30 long. Went from 6 t5s on a 75 to a couple compact florescent to 4 t5s over the 30 long they are in now. That is the only variable I can come up with but does not seem like it should be the problem. Any ideas?

 

[marinesnow]

When you downsized, is it possible you went through a mini cycle that’s now over? Any other corals/fish show stress? Ammonia destroys corals in my experience.

Also check flow, blastos like less.

If things are back to normal, I’d give it some time to heal. If it doesn’t appear to be healing day by day, then I’d recommend a large water change.

Another possibility is allelopathy. If you transferred soft corals to this new tank, the stress could cause them to release biochemicals that kill other corals. Carbon and/or water changes would help remove them.

Next, a fish or predator could be eating it when you’re not looking.

Last, I’d try to lower your nitrates to at least 15 with some water changes.

Good luck

 

[Ocean Lotion]

I did move a large green finger leather that I ended up cutting off its rock and then rubber banding to a new rock which cut through it. The leather gave off enough nasties to make my skimmer go crazy for days. Nothing else including sps were effected though. Maybe that stressed it and is where it started. I had forgotten about that. Thanks.