what's going on?

[Jase]

A little background...I have a 55 system, lit by 4x 96 watt pcs. It is just over two years old. It has a 30 g sump/refugium, with a 3 inch sand bed and a bunch of rock with caleurpa.
Everything has been growing well.
Now, about a month ago, I lost nearly all my caleurpa...some kind of mucus was covering it, accumulating at the water surface, and covering the rock. It still is.
My sps slowed their growth considerably, and several have developed blisters, though polyps still extend through them.
I have been blessed with a plague of xenia for the past 18 months, throwing it away on a weekly basis. Last week nearly all of it crashed.
No nitrates, no phosphates, Calc 400, alk 3.5, temp 80, pH 8-8.2.

I did a 60% water change two weeks ago. Nothing doing.

I'm stumped.

 

[jmeader]

Physically remove as much of the mucus as possible. Increase your PS if possible. And use carbon for a few days. I think your having a bacterial bloom similiar to cyano.

 

[BReefCase]

If you mean you had Caulerpa taxifolia, I believe that it "went sexual," as reefers call it, collapsing as part of its normal reproductive life cycle. This is no problem in the ocean, but is bad news in the small water volume of your tank.

This sudden collapse will indeed release all sorts of undesirable stuff into your water, including all the organic nutrients that it normally binds up as it grows, and which you export from the tank when you harvest excess macroalgae.

The collapse can be caused both by time, i.e., the age of the growth (two years is certainly old enough) or it can also be caused just by over-harvesting of the algae.
If you recently pulled a lot out and took more than about a third of what you had, this can definately cause the remainder to collapse.

Use a number of partial water changes and run activated carbon now. A good protein skimmer is necessary here, too. A bacteria bloom may indeed have followed the rotting macroalgae.

Be careful with this stuff in your tanks in the future. Anyone who lets Caulerpa taxifolia grow in their tanks needs to watch it, and trim it regularly in small amounts -- don't let it grow too much, and don't remove too much of it all at once.