montipora bleaching while others are fine?

[bwalker]

i have 3 types of monti and until 2 weeks ago all are fine but the red one. it is bleaching(dying) temp is ok 78-82, all water parameters are fine but alkilintyis 90(low), ca 400, trace of phosphate, and nitrate, all others 0 ppm. this coral has been in tank for over 1 1/2 years and grew from 2" frag to presently 18" diameter, it sits right under 250w mh, which i change mn's once a year, changed 3 months ago, 4x 03 actinics changed every 6 months, 90 gal tank. i do 25-30 water changes once a month with ro water. and i even tried a huge water change 4 days ago 65 gal change only left about 2 "of water in tank.what is weird everything else is fine except 1 acan which i also have had for 1 years. please help me with this problem ihave tried everything i know to try and have talked with localpet stores and just don't know what else to do. thanks in advace for all you help and replies

 

[ReefLady]

Everything sounds good...hmmm...

Is it bleaching from the top down, or bottom up? Is it simple bleaching, or does the flesh/tissue seem to be 'sloughing' off? No trace of brown jelly/goo? Any changes to the tank / new additions? No pest seen - flatworms, nudibranchs, etc? Is it a cap or a digitata (or something else)?

 

[Frankie]

As soon as I read this I too thought of nudibranchs. Could you post some pictures of the corals please.

 

[bwalker]

i don't see any nudibranches at all, it is bleaching from top outside edge inward. no slime or goo. mainly discoloration. only thing adedto tank in last 6 months was 2 shrimp to eat aptasia anenomes. i will try and put some pics on here later today. thanks for all your help

 

[ReefLady]

Pictures? Has it gotten any worse?

 

[reef dummy]

This is weird, my orange monti just did the exact same thing. Bleached out of the blue and totally died. All other corals doing perfectly fine. I managed to save a few small pieces and place them elsewhere and they seem to be doing good.

 

[MidWest Frags]

Montipora's, especially digitata's are more susceptable to salinity changes than most SPS. Just a thought.

Also I would get a magnifying glass and closely check out the dying edge of the Cap. The nudis are bright white and sometimes blend in with the edge.