Here is a thought, where did you get your rock from? Is it full of phosphates?
I got live rock from a guy running a Fowler years ago and had super high phosphates for 5 months. Would test see it low like .02 but gHA would be growing endlessly everywhere with that much GHA feel free to assume your available phosphates (from feeding) and from rock are much higher than your test kit shows (fwiw carbon dosing much easier than trying to grow macro imo and you can dose nitrates with carbon to limit phosphates). The GHA is using up the excess phosphates when they become available so they test low but you are supplying way to much with that much GHA
Please Remember all tanks are growing some hermit crabs and snails are eating it if you are totally out growing their consumption something is off to much food not being eaten or something look at that
I’m going to go against the grain here a bit.
stop doing water changes for at least one month
you use an ATO so you shouldn’t have any salinity swings
First focus on your doser and test your alk and calcium every two days at the same time of day to figure out your dose use the same test kits the same way every time (even if you have small user error and you calcium is 440 instead of 430 no big deal)
then spread your dose throughout the day
for example if you dose 20ml of alk per day do it 5ml every 6 hours so tank alk is stable all day not 8.2 to 7.8 slowly over 24 hours then spiked back to 8.2
get both calcium and alk stable for two weeks this way then start checking every week
After a week if you have dropped over say .2 alk raise up your daily dose by using
BRS calculator to figure out how much (catch up dose divided by 7)
The problem with your huge water changes is if you are doing 15 gallon water changes every week is you are most likely causing to much quick change
for instance your alk goes from 8.4 to 8.1 right now cause your salt mix was alk 9.0 and your tank was at 8.0
then your calcium goes 450 to 430 right now
these are major swings like buying a coral from a store and putting in your tank
for your next monthly water change after you have kept major stable for a month test your tank for the three major
then test your water change water then make them match
also make sure the temp is the exact same
then do a water change
I just get the sense things are not as stable as you think
the ocean is so much water it can not change quickly to get sps to grow and thrive your only goal is to keep things stable all the time
if things move to often you won’t get growth if they move to often some more things can RTN or slowly die
it’s possible you have something else going on like bacteria but I would guess one coral had a bad reaction to N and P moving fast or from constant changes and
then you started chasing the problem and every time you change something, a light setting, an power head schedule, move a coral from one spot to another in the tank rearrange rocks, ect, ect. You are not providing a stable environment.
think about it like this if you planted a tree in your backyard in a pot and then every couple days moved it from direct sun to shade to partial shade to direct sun and you watered it ten gallons today 1 gallon tomorrow ten again then no water for a week then ten gallons again and constantly changed how many nutrients were available for it to grow what do you think would happen to this tree?
Think stability I feed one cube and one sheet of nori everyday and dose ab+ Daily Once a week I do a second cube and feed anemone and coral I do different kids of cubes but I put in approximate the same amount of Phosphates most every day
lots of hermit crabs (one per gallon plus some snails) to eat the food the fish don’t
when I buy a coral from the store it sits alive for 1-3 months then it starts to explode in growth
pick a setting you like find a home for corals and then stick with it
