Bubble Trouble

[trilinearmipmap]

I have had a bubble coral for about a year. It has always thrived, it has grown to 10" or 12" across and it was a showpiece coral in the tank.

Over the past month or two the coral has done poorly, it does not expand up, it stays contracted all day and does not look good. All the fish and other corals in the tank are doing great. It is a mixed reef with LPS and some zoanthids, mushrooms and soft corals.

The tank specs are: 120 gallon, 432 Watts T5 lighting, moderate circulation, Temp 81 degrees, pH 8.2 to 8.4, Ca 380, Mg 1400. Alk was low for a long time and I recently added sodium bicarb and sodium carbonate and I overshot the alk high. No nitrates, nitrite or ammonia measurable.

There are a few possibilites I have thought of for this coral doing poorly, I just want some opinions on this.

1. It could be the alk problems which I am trying to sort out with water changes.

2. It could be a depletion or excess buildup of unknown chemicals or nutrients in the tank - I am trying to sort this out with water changes.

3. Someone could be trying to munch on the bubble coral - whether my Copperband Butterfly, or perhaps a worm or crab in the tank - I have not seen this happening though.

4. I stopped feeding the coral for 2 or three months to sort out some problems with Aiptasia I had before - but the other corals are doing fine without feeding.

6. There is a large Frogspawn nearby, I have not seen any sweeper tentacles come out.

7. There is a cabbage leather and a colt coral nearby - however these corals have all been in the same spot for ages with no problems before.

Anyway I am working on water changes and trying to optimized water parameters for now, any input on this would help a lot. This was my favourite coral.