Ok, so two things: I hate to tell you this, but the mandarin is not going to survive in your tank unless you are adding large amounts of copepods at least twice a month if not more. I’ll put it this way: I would love to keep a target mandarin, which are on the smaller side of mandarins. I have about 60 lbs of live rock and I’ve added multiple pod mixes to my tank. While I do have a pretty healthy pod population right now, I’m certain a mandarin would wipe it out and frankly, I wouldn’t keep one in mine unless I was prepared to constantly restock pods and even then I’m not sure that would grant long term success. If you can afford it and don’t mind adding lots of pods, they can help in your algae control but this is a whole other topic.
To get back to your corals health, I would put my focus on getting your alk up to an acceptable range and make sure your ph is staying in an acceptable range for your corals. This could be why you’re seeing your corals detach from their skeleton. That’s exactly what happens when we talk about ocean acidification and coral bleaching in the wild! With low alk and ph you’re riding a razors edge of acceptable limits if not below that which your corals need to survive.
To help with your focus on algae, let me share something anecdotal. I was growing GHA like crazy, and honestly wasn’t too worried about it because I would rather grow GHA in my display than have a host of other issues like cyano, or Dino’s. Anyway, I have a fish (that will remain nameless because I don’t want other people in the hobby to jump on this as a solution for GHA, because it’s not), but I have a fish that was only eating GHA no matter what other food I offered it. It ate all my GHA. It definitely had help with some CUC but I could see this fish wipe out patches of GHA every day until there was none. Since I couldn’t get it to eat anything else, I just kept dumping food in to purposefully fuel GHA growth so this fish would have something to eat. Just a week ago, I finally found a pellet that this fish LOVES and it has put on some substantial weight now that it’s not eating only GHA.
So now that I can feed food that actually gets eaten, I’ve cut WAAAY back on feeding and I’m getting my nutrients under control.
During the time I was purposefully fueling algae growth, I have had all of my sps corals exhibit new growth, with GHA touching the frags at times or growing right next to it. The corals are healthy and my CUC and fish just eat the algae off. I do think some of my corals were stressed due to overfeeding and high nutrient levels, but at no time have I lost tissue on a coral, and especially not to algae growth, in fact I’ve seen the opposite as I watch my corals grow over places that were once covered in GHA.
What I have made sure of is that my alk, magnesium and calcium are at acceptable and stable levels, and especially pH.
These are my rocks right now with almost no algae
Vs 2 months ago:
So what I’m saying is try not to sweat the algae and focus on coral health. I can post some before/ after coral growth photos if you want.