Good morning everyone about six months ago I converted my fowlr into a reef tank. the very first coral that I bought was a xenia, when I got the xenia it was two colonies attached to a piece of rock since then I has grown to 4 colonies and was doing very nicely. Now the problem started 3 weeks ago when I noticed that my nitrates were high 50ppm

. I started to do weekly water changes and have gotten my nitrates down to 15ppm another thing that I did was upgrade my
protein skimmer. upgraded from seaclone 150 to aqua c remora pro with mag 3 the problem is now only one of the xenia colonies seem to open and the other 3 only open a little

. I've read on this forum that xenia like dirty water so was it a bad idea to upgrade the skimmer or what can I do please help. My parameters have been stable nitrite o ammonia o nitrate 15 ph 8.3 salinity 1024. calcium 400. also my other corals seem to be thriving.