I'd check, double or even triple.check the following when having issues:
Salinity no harm recalibrating with saltwater solution to make sure.
Alk, ph salinity temp swings past 6 months as I feel after a swing corals can still show signs till weeks or months after before they recover or are lost
Rodi is it 0 tds ? Worth sending a freshwater sample to icp check for contaminants.
Changing ur ro prefilters and checking tds past Ro membrane and past DI Nd making sure this is OK.
There was mention of alk swing from 7-12 that can shock the system for months.
Alk swing of 1 in 3 days to me is a big swing even if it is in the right direction.
Coraline die off is a sign something happened but need to pinpoint it (coraline goes white when exposed to air like in a water change so that might not be an issue.
Icp can help
Checking magnets in pumps or glass scrappers for one that might have gone bad and exposes rusting metal to ur water.
How do u lose ur corals ? Do they rtn, stn , stn from the base dry off ...?
Where do u get ur frags from ? Healthy frags ? Fresh cuts ? Established frags before purchasing ? Do u dip them before adding to tank ? Might be simple shipping stress or stress from a rough dip that's killing them and not ur tank.
How long did u have the frags before they were lost ? Any chance or signs for any pests ?
A larger water change with 0 tds water might be a good way to offset any parameter that drifted or any contaminant that went in the tank.
Reducing light intensity and dosing when corals aren't doing well as I believe intense light can stress them also corals when struggling won't consume like usual which causes ur levels to raise. Pics of ur setup and corals would help.
Wow there is a lot in there I’ll try to answer them all I might miss a few haha
A. Salinity was checked 3 separate sources at my house and also checked by two other local reefers all got 1.025
B. I haven’t had a major alk swing in over 4 months the last being where I went from 8-11 I’ll check my notes to confirm. My alk consumes slowly.1 every few days so I test once a week and dose Red Sea according to do minor adjustments lately
C. TDS is definitely zero . I switch out my filters and membranes frequently. I was running 1 tds for a month or one water change during that time I was told 1 tds is not a major concern other then that it’s always zero
D. Coral die off . I guess I should have been more specific. The rocks are still covered in coralline. Lots on the back wall with spots of white so maybe like you say from water lowered from water changes exposing to air ? Most of the die off is in my sump where I don’t always turn the light on anymore cause I gave up on trying chaeto 0/2 on attempts even though I always had nitrates for it to consume lol
E. No magnets in the tank my map 40 magnets are external unless the pump must have some inside to hold on to the outside as well ? I don’t know how these pumps work to be honest lol
F.I’m not advanced enough to know what rtn stn are ? To me corals are healthy dieying or dead . They were healthy before I removed them from the tank glued them to a rock and placed back higher up in the tank
g. I wouldn’t know if they were fresh cut or healthy they were online from Ontario under wysisyg . They looked good online and looked the same in person?
h. I do acclimate the corals to lower lights 50% over 15 days increasing to normal lighting
I. I just made 30 gallons new water last night and I’m testing all the peramiters in it Monday night to give results to
@Randy Holmes-Farley so we can see if the bucket peramiters match what I’m measuring in my water changes.
I think I answered them all I probably missed a few haha