Practical zooxanthellae question

[ATJ]

I currently have an Acropora sarmentosa that is bleaching and I want to know the best course of action.

I have had the colony since the end of last year and it had been doing extremely well. It was growing and generally looked very healthy.

A couple of months ago I started having algae problems in the tank it is in. The algae was mostly dinoflagellates and diatoms and this lead to the demise of most of the snails. The surviving snails were moved to another tank. The algae bloom appeared to have no affect on the scleractinian corals (Inhabitants), but the soft corals, zoanthids and corallimorphs looked worse for wear. The only change I noticed in the A. sarmentosa was a general browning, which I put down to an increase in zooxanthellae population.

Over the last couple of weeks I have finally got a handle on the algae bloom. The main things I did were: A complete cleaning out of the sump, left the MH lamps off for 2 days and increased the alkalinity from 2.9 to 3.5 meq/L. After leaving the lamps off, which was the weekend before last, I started with the MH lamps on an hour in the morning and an hour in the afternoon, and have been adding 30 minutes each day. I am now at 3 hours in the morning and 3 hours in the afternoon.

Last weekend, the A. sarmentosa started to bleach. The bottom 2-3 cm are bleached and I think much of the tissue has died back. The top of the colony started to bleach on Monday,

so on Tuesday I put a piece of shade cloth between the lamps and the colony and it has stopped further bleaching. However, the tentacles are no longer expanding.

What should I do now? Can I save this colony?

By the way, all other inhabitants are looking good, with the exception of some zoanthids which are still closed up much of the time. The Sacrophyton sp. is open most of the time and so is the Isis sp. Both are looking very healthy.

 

[Eric Borneman]

Andrew. Keep the shade cloth there. If the bleaching has stopped, its about all you can do. I would do water changes, too, in case there are dinoflagellate toxins still present that are bothering or causing the bleaching event. Nice pictures.

Eric

 

[jamesw]

I don't know Eric. I think Andrew has confused a tissue peel with bleaching. That picture shows a tissue peel.

Andrew: There is pretty much no "cure" for that, except for fragging the coral and moving it to a different (isolated) system where it can't affect the other corals in your tank.

HTH
James

 

[ATJ]

James,
I have both tissue peel and bleaching. The centre of the picture is definitely loss of tissue, but the rest of the colony is much lighter than it was previously and looks much more granular.

Eric,
I don't think the bleaching (and tissue dieback) has been caused by dinoflagellate toxins. The colony was fine during the height of the dino bloom and only started to go downhill after the dino susided and all other tank inhabitants started to look better.

I am very worried by the fact that the tentacles are no longer expanding. Previously, they were expanded day and night.

 

[Eric Borneman]

James and Andrew:

I looked at the pictures and it looked like bleaching, although if there is tissue loss, I concur with james. The white skeleton is so reflective, but the hints of pigment left around the polyp and coenosarc looked to me like there is still tissue pressent, and with polyps withdrawn. If tissue loss, see above post by James. If tissue present, see above comments by Eric.

Eric

 

[ATJ]

The colony didn't make it.

It showed all the classic signs of "RTN".

I made 6 frags of which 2 have already gone the way of the main colony. and 3 others don't look great. No other corals in the tank look anything other than healthy.