[demifelix]

I have a large Colt coral for a few months now, and it's always expanding to 1 foot wide and 1 foot tall during the day. However, for the past 2 months, it's been receeding, and now it only stays at about 4" (both length and width). I thought it was readjusting itself during this time, but now I really think something is wrong with it. The tiny polyps never closed all the way as before, and they never opened fully either, but they always stay half-closed all the times (day and night). Can anyone please help me with this? This used to be a very beautiful piece, and I will be very sad to loose it. All my water parameters seem to be ok: nitrate 0, nitrite 0, pH around 8, calcium around 400.

[Reefland]

demifelix,

It could be 1 of a hundred different things, maybe it's nutritional requirements aren't being met? What kind of lighting is the coral receiving? Do you add any supplemental foods?

[demifelix]

I have 3 175 W Metal Halide 20K 8-10 inches above water surface in a 150 gal tank. The Colt is in the upper third to get the most light. I add Black Powder and Kent Marine Micro-Vert maybe once a week. I also add Trace elements, together with Iodine, Strontium according to instructions. I used to add baby brine shrimps, but since the polyps are not open now, I can't feed brine shrimp anymore.

[Reefland]

Do you test for Iodine and Strontium? Iodine can be toxic at elevated levels, most tanks get more than enough Iodine from foods added to the tank. This might be a possibility.

[demifelix]

How do I test for Iodine and Strontium? I took my water to LFS but they don't provide either. What is the recommended levels of these? Also, I have leather finger, bubble, hammer, mushroom, star polyps, frogspawn, and everything else is doing great. Thanks for you help.

[ghofmann]

You can get test kits for either iodine or strontium from online sources or from your LFS. Salifert test kits are generally accepted as one of the best you can get.
I believe that the acceptable range for Iodine is 0.02 to 0.04 mg/L and Strontium is 5mg/L to 15mg/L

A good rule of thumb is to never add anything that you can't test for.

I had something similar happen to a colt coral and could not figure out what was going on with it. Finally I rearranged the rockwork and the colt started opening and making a comeback. The only thing I could figure was that my green star polyps were a bit to close and it was affecting the colt somehow.

[Reefland]

Good points on the tests and the placement in proximity to other corals Greg!

[demifelix]

Hmm, actually my green stars are nearby my colt, never thought about this. I'll get some tests done on these and will let you all know the results. Thanks.

[AquariumSpecialty]

It could be several things (as mentioned already). One other think to check is your temperature. It has been my experience that Colt Corals are pretty sensitive to temperature changes. In addition to the other suggestions, take a look at your temperature swings.

[demifelix]

My temps are around 81 with lights on and 77 with lights off. I maintain a chiller to keep the temps in this range. Do you think the temps are ok?

[AquariumSpecialty]

[quote=demifelix]My temps are around 81 with lights on and 77 with lights off. I maintain a chiller to keep the temps in this range. Do you think the temps are ok?

Yes. You should ok with that but you may want to consider narrowing your range if that is possible with the chiller you have. The controllers we use keep the ranges a little tighter. I doubt temperature is your issue in this case but I thought it might be worth a look. Good luck. If you can't figure it out soon, hopefully you have a friend who can temporarily keep the coral for you but no guarantees on that either...

When dealing with multiple variables it's difficult to sometimes find the solution. It's not an exact Science but it keeps the hobby interesting and unfortunately sometimes frustrating.