LPS not doing so well

Hmm, out of ideas. But I don't understand why you'd be seeing a GHA outbreak without an obvious source (based on the info/numbers you've provided).

Swap out the carbon and test for Mg as soon as you can for now.

 

I'll try my best on getting that Mg test kit asap.
I was too lazy to change out my carbon so I forgot. I didn't know that it would have an adverse effect.
I started vacuuming the sand bed whenever I do a WC and I thought that was causing the GHA outbreak.
My nitrates and phosphates are low. I feed every other day so I have no idea what else could be causing the GHA.

 

Just swapped out the carbon. I will have to do some searching locally for a Mg test kit. I hope I find one today.
But, can someone enlighten me on the effects of low or high magnesium. I've never done much research on the topic.

Also, I thought I'd add that only recently coraline algae began to grow. Isnt this a sign of good Mg levels?

 

It would seem to me since you are changing that much water "10% weekly" and if you are using a decent salt magnesium would not be an issue. Unless you have a huge bioload of fish changing the carbon every two to three weeks seems like over kill to me as well. With LPS you can run the water too clean. You are changing water routinely, skimming, and changing out the carbon frequently so I would look either to parameters and possibly you running a tank too clean. Your bulbs are not old so there goes that. Phosphates are getting into your system if you have GHA so I would be concerned about that then magnesium at this point. If you can post a pic of some of the corals that would really help. JM2C;D

Ahh just saw parameters, forget about that, they look fine.

 

The best Mg articles I know of:

Chemistry and the Aquarium
Reef Aquarium Water Parameters by Randy Holmes-Farley - Reefkeeping.com
Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com

 

I'm leaning more on PO4 as well. I only have one test kit so I cant confirm accuracy this is why I intend on either getting the biopellets or I've heard that Vodka dosing could help as well.
hare are some before and after pics:

 

:/ Things may be too far gone here.

Also, vodka dosing can promote cyano, fyi.

 

The open brain is my favorite piece. I've had it for about 2 yrs now. I really don't want this one to die.

 

Well the dented brain is a complete goner and probably the same for the favia

But I'm hoping the open brain, bubble, torch and frogspawn make it through.

I had no idea about the cyano associated with vodka. I'll just use the bio pellets then.
Haven't tried either as yet.

 

The open brain looks bleached and I can see the slow tissue regression on the others. Is it possible the brain bleached when you changed out the bulbs 5 months ago ( photo shock )?

Many LPS reside in less than perfect water conditions in the wild and can be found in turbid back reefs and shollower water. I strongly suspect that you are over polishing your water secondary to the slow decline and the information you provided.

I would cut back on the carbon use and reduce the time the skimmer is running. Doing a 10% weekly water change is going to replace all trace elements so if you are dosing anything I would reconsider.

As they say nothing good happens fast in this hobby so I would make small changes slowly. I think that if you allow more nutrients into your system you will see a gradual improvement in the LPS.

Unless you are running a system dominated by souley SPS you do not need to polish the water as aggressively.