Seeking advice on coral care

[starfisher]

I'm having a tough time with most of my LPS in the tank - the flesh is receding from the bottom up, and when it gets to the top of the skeleton, the coral just kinda melts away. I'm stumped. The corals that are having issues are my frogspawn, hammer, acans, dendros, and bflintix9tos.

My levels are as follows: KH is 10.3, which might be the problem, CA is 435, MG is 1420, and phosphate is 0.00 according to my Hanna checker.

I've got a pretty diverse tank, with two rose anemones that are thriving, a mini maxi that's not so mini, a maxima clam that's doing incredibly well, duncans that are doing great, zoos that are fine, a hurricane chalice that's doing great, a lobo that's fine, and a walking dendro that's doing well too. Most of my LPS have been in the tank for at least six months.

My fish have been in the tank for almost three years and don't bother anything - they get fed every day and are way too fat. I just added a purple stylo about a week ago, and it seems to be doing fine so far.

[microb]

I'm thinking a nipping fish might be the culprit, but it's weird since your fish have been in there for years and haven't bothered anything before. That high alkalinity isn't necessarily a problem if it's stable, though. I'm more concerned about the zero phosphate reading - that could be an issue. Have you messed with the flow at all? Too much light might also be a factor. Think back to any changes you made before this started happening - even small stuff like adding carbon or something.

[starfisher]

I was away for a few months, came home to do water changes, and that's when everything started going downhill. The new corals I added recently seem fine, but they haven't been in long enough to be affected by whatever's going on. I did switch to LED lights, and I reduced the flow in the tank.

[microb]

Are your LEDs dimmable, by any chance? Too much light could be the culprit. LEDs tend to focus light intensely, like a magnifying glass, whereas traditional bulbs spread it out more. I've seen it happen to a lot of people - they switch to LEDs and end up over-lighting their tank, which can be disastrous.