Two months ago I upgraded from a 12500K bulb to a 20000K XM. A week after the bulb change I extended the photoperiod from 10h to 12h over a 1 week period. The light is 8" from the surface, and the tallest coral is 7" from the surface.
Tank inhabitants:
Euphillia sp.
Tubipora musica (mother colony 6" and naturally fragged piece, 3 months old, grew from 12 polyps to 2" across)
Blastomussa wellsi
Acropora spp. (5 frags, .5" - 2.5")
Montipora digitata (3 frags, 1"-5")
Porites sp. (small massive w/ christmas tree worms, 4")
Xenia sp.
Pocillopora damicornis (.5")
Stonogobiops yasha (2 pairs)
Alpheus randalli (5)

Everything was going great, after the light change colors improved greatly. Growth was very visible, calcium and alkalinity use was high, I was dosing 25ml of Randy's 2-part Ca/Alk daily. Then I noticed some top-down bleaching in one of the Acropora frags (took 3 days to go from peach to white), and then another. Ca/Alk demand dropped to zero. I immediatly cut photoperiod to 4 hours. Fearing alleopathy I started running carbon which I change every 5 days. Polyp extention was then way down across all corals, Xenia stopped pulsing for first time, Tubiporas have most all polyps closed almost all the time. Non cnidarians are doing very well, mysid shrimp and pod populations are very high, an Alpheus randalli was spotted carrying eggs (see Dr. Ron's forum for pictures).

I have been feeding frozen baby brine, cyclopeeze, and Phyto-feast, trying to nourish bleached colonies. I will have constant supply of live artemia set up this weekend. I think the bleaching has stopped, but polyp extention is still almost non-existant on all corals, save the Euphyllia and Porites, which shed just after bleaching began (it does this monthly or so), but has since had perfect polyp extention 24/7.

Please help!

Thanks.

You have (by any definition I know of) an obscene excess of light over this tank and you are also likely seeing (predictably) the signs of photoinhibition from corals suffering under it in time. This is a very common (query and time frame) problem.

Too many folks fail to understand the relationship between zoox and their host, and believe that "excess light" will be expressed as sudden bleaching. Not so. The effects of photoinhibition can take weeks or months as you are seeing. And the behavior of the coral (positive as it seems) need not reflect the "heal;th and wellness" of the zoox that fail eventually (shut-down/bail-out).

At most this aquarium needs 150watts of light and thats without a low to med light collection of cnidarians as you have assembled. 100-125 watts would be fine instead.

You need to change the lamps (to lower watts) my friend or raise the light much higher (and waste electricty...ughh) to suceed here IMO.

.

Anthony Calfo