Dying/Shrinking Corals

Ove rthe past few months I have watched a colt coral go from 8 inches to a pinched up 2 inches and a frag of polyps go from an intense aray to just a few tiny ones. I'm at work so I can't provide details but my water parameters all are excellent. Over the last 6 weeks or so I have increased water changes to about 30% just to make sure the trace elements that the salt provides are being replenished. Plus I have been feeding regularly with phytoplankton. But to no avail. Any suggestions are greatly appreciated. I figure these guys only have a few weeks at best.

 

How old are the bulbs?
Have you made any other changes?

PS....colt corals don't eat phytoplankton.

 

Neither do polyps for that matter
What is the lighting? Flow situation?

 

I have two koralia 1's , flow is OK. The colt was about 4 inches offset to the flow. I have 10000 k and actinic t5s (one each) that were both changed in about June just to make sure that the lighting was OK. The colt is located about 5 to 6 inches below the lights. The polyps a bit further. I had not made any changes prior to when I started to notice the problem. However I did remove bio balls and replaced with live rock rubble in about February March to try to reduce nitrates. I have gotten my nitrates down to 10 to 15. It

 

what about other params? po4 over time will have a big impact of corals...you have a a decent size bioload, could it be that your overfeeding? the nitrates are staying in check buy not the po4

 

In all these large water changes you've been doing - has the salinity/SG of the tank, or the temperature of the tank varied at all? Sometimes if you alter the temp or the salinity abruptly, corals get unhappy.

 

i also have colt coral. mine appears to do the same almost daily. my water params were not the best for a while but now they are good, but my colt coral will still occasionally shrivel up. its just a moody coral i guess. lol is it a possibility that something is bumping it? my hermits seem to love to bump my corals and watch them close up. very easily entertained creatures hermits are. good luck!

 

Well your flow is very low, so that's probably not helping. Again, what type of lighting and age of bulbs? Your other parameters?

 

lighting is t5 one 10000k and one actinic. parms are o nitrite & ammonia. nitrate 15, ph 8.2 sg 1. 022, temp 76.5, calcium 440, phosphate 0, magnesium 1350, these are pre water change and are typical. i do use treated tap water. lfs said this should not be a problem since our city's water quality is good. was thinking of moving corals to an existing 29 gal tank with similar parms and use lfs water to do changes.