Okay the tank looks nice but definitely looks very new; only four months old. It needs more time to mature. At this point fish are easy because they just need clean water, but stony coral are difficult because they need a more mature tank. Soft coral can become stressed due to a change in lighting from one tank to another and going from one tank to another because of the change in the water and the environment. I'd suggest reducing the photoperiod or turning off a couple more lights for a few weeks.

You didn't say whether GFO or AA are being used. If so, I'd suspend their use for a little while and let the Refugium algae do it's job. 

Here is a rough drawing of one way to set the light at any elevation using multiple zip ties chained together. A screw put into the top of the stand is the short black line. Purple and blue are two separate zip ties holding the clip-on cone reflector light drawn as black. I use a $3 twist PC light the highest wattage possible in daylight color. It's the best light for the money, even better than LED's.

Aloha,

Mark  

The color is okay (5000 Kelvin) but just as important is the intensity. Some hobbyists I talk to don't have enough light over their Refugium. The distance of the light from the algae really impacts intensity. I place Refugium lights as close to the top of the water as reasonable (with the pump off, of course).

Before we get too far off topic, lets go back and look at the original issue. Coral looking poorly. Which coral are we talking about? How long has the tank been set up? May we see a pic of the tank?

Looking again at the OP, a Ca level of 400 is not low. It is totally within range. Also, I just realized that I was a little too quick to judge. It looks like Nitrate had been running at 5 ppm but had risen to 20 ppm, right? 20 ppm is not high. It is a totally acceptable level, but sometimes any amount of increase (or decrease) can cause coral stress. Not serious stress. If that's all it was, they should be happy again in a few days.

The Reefkeeping Tips are a compilation of discussions/opinions by hobbyists here on the forum on the specified topics. They deal with a lot of issues that new hobbyist come up against. 

To quote an old friend, "Keep both arms in the tank and enjoy the ride."

Aloha,

Mark  

Mark, I should clarify some things  First, I do have a 5000k bulb in my refugium that I keep on at night. Actually the reason I increased the feedings was not for the corals sake but for the macroalgae. I was talking to another reefer about how all my chaeto gradually disappeared after about a week or so of putting it in.  My nitrates and PO4 have usually been close to 0, so he suggested maybe I feed a little more so that the macro had a little more to grow on.  I still don't feed that much where a ton is settling on the bottom.  Based on what I've read online it sounds like the tank can be a little too clean in regards to macroalgae. As for mixing new saltwater, I don't have the time or patience to let the saltwater aerate forever and heat up to match my tank temp exactly, so in my limited experience, I have found what you say to be true! I would love your info about feeding your system and I also am going to try reading all your reefkeeping tip posts asap.

Coincidentally today, a coworker that has seen my coral farm, asked me about my secret for growing coral. I'm not sure I have any secrets, but my answer to him was that I feed the entire system and let the system feed the coral. Let me know if you want more detail about feeding the system.

Regarding mixing saltwater:

1) Most hobbyists don't realize this, but as much as a 10 degree temperature difference doesn't matter. I've done it enough to know. 

2) Newly mixed, well stirred salt water can be added immediately. I've used 5 gal buckets where I pour the salt water back and forth a few times to aerate it before pouring into the tank, taking care not to pour directly on a coral. 

Oh, and one more thing... The RDP Refugium should have a large growth of Macroalgae illuminated all night (16 hours) with a bright light or it cannot do one of it's main jobs, that of reducing pollution (Ammonia, Nitrite, Nitrate and Phosphate).

Aloha,

Mark