This guy started to STN/RTN (somewhere in between...) about a week and a half ago; it was also located in roughly the same area as an acro that RTN'd while I was out of town a couple months ago. I checked parameters to see if I could find anything and everything was right where it normally is with the exception of salinity which had dropped to roughly 33ppt (pretty much right on 1.025 for my refractometer). The Copps undata was showing signs of stress again which is what caught my eye first (I never seem to be able to keep that one happy for long so it's a constant struggle). I brought the salinity back up to 35ppt via salt water in the ATO over a few days and did my typical 10g water change last weekend. The acro has stabilized the past two days and has started to color back up a bit too (was browning out but has a lot of green back today).
Things that were different the last few weeks:
Light intensity (raised and lowered to accommodate various issues)
Salinity dropped slightly (35ppt to 33ppt) but quickly during a water change, skimmer, and reactor maintenance (not enough salt water was replaced to account for the lost displacement)
A couple water changes were conducted using Live Aquaria's salt but I'm out of that so back to Reef Crystals (the only other salt that has been used in this tank) for another week or two until that is all used up and then shifting to regular Instant Ocean.
I'm also wondering if there may be a trace element issue as I cant find anything in the standard test results (alk, Ca, Mg, PO4, NO3) that would indicate an issue. I submitted some results to Triton on the 5th but my results were:
SG - 1.025
dKH - 7.9
Ca - 450
Mg - 1365
PO4 - .058
NO3 - 2.5-5.0
We'll see how the Triton results look sometime next week when the results come in but the only thing I expect to be different is PO4 which will likely come back at 0 or very close based on previous Triton results as compared to what my Hanna ULR shows. I have a calculator that will provide some results in regard to salinity but I've never seen that off by more than .25ppt between my refractometer and Triton.
In regard to trace element depletion, I've decided to do weekly 10g water changes (roughly 10%); to that end, I changed 20g two weeks ago and 15g last week I believe. Tomorrow will be a typical 10g change which is what I normally do (though every two weeks vice weekly).
I have no clue what has caused the issue but things have at least stabilized at this point so I guess that is a win (for now). I'd hate to lose another coral and this little acro was pretty awesome.
