SPS bad response from regular water change. Actions to take?

[PhilM]

I just completed my bi monthly water change on my RS Peninsula 650 mixed tank and several of LPS corals acting poorly. I have attached pics of some Candy Canes and 2 Hammers that look damaged. Similar others near them are doing fine. My toadstool, devil's finger, and a plate have pulled in their polyps, but his has happened before and they come back quickly. The system has been up for 18 months. I do a 35 gal change every 2 weeks. The circulation pumps are off for up to 90 minutes max with powerheads circulating during that time. Temp and salinity between tank and new water generally matched relatively closely (0.5F and 0.3ppt). This is the first time I have had a significant reaction from some of my lps corals. No noticeable effect on SPS, softies or fish. The only big change was in ORP (332 to 208, now back to 299) which usually occurs on the water changes. Any ideas on actions to take would be appreciated. Thanks in advance, Philip

 

[shakacuz]

unless things are dying, do not do anything. water changes usually cause a swing in something unless you have an automated system or good maintenance. monitor for any negative changes that occur other than some corals being closed.