Because we can tell whether the N pollution is a problem just by looking at the coral and the tank in general, the most important tests that we use are Alk, Ca and Mg.The best three test kits for the money also happen to be the least expensive. It's the Red Sea Reef Foundation(Alk,Ca,Mg). On Amazon right now it's $51.33 with free shipping. A really good thing about it is that the refills are about $15 so we don't have to buy the whole thing again when all we need is more Alk tests. See if this link works:

http://www.amazon.com/Red-Sea-Reef-Foundation-Test/dp/B004FUJ5NE/ref=sr_1_1?ie=UTF8&qid=1461617125&sr=8-1&keywords=red+sea+test+kit+pro

I would not get any Stars at all right now in that tank. Here is a recent thread about Blue Linkia.

http://utahreefs.com/forum/forum_posts.asp?TID=79684

Mandarins need live food and plenty of it. Feel free to search the many discussions that have been posted here about this topic too. The live food I'm speaking of is that growing in the system. Buying live food is prohibitively expensive. With all the Damsels and the recent week of no feeding, there are very few live bugs in the display tank. I would not recommend a Mandarin in that tank. In fact, that size of tank is the bare minimum size that could reasonably support a Mandarin's live food needs.  

BTW, If you are looking for ideas for your next fish, consider the Clownfishes(of course), the Blennies, the Cardinals, the Wrasses, the Pygmy & Dwarf Angelfish, the Rabbitfishes and the Tangs. Remember the Assessor that Ross was so proud of and how cool it was hanging upside down under the huge Blue Wall Hammer Coral? That fish along with the Royal Gramma or the Pseudochomis would also do well as a next fish.

Aloha,

Mark 

Mg is well within range.

What I recommend is what a lot of us here use. The chemicals and how to do it is discussed in the Reefkeeping Tips thread linked below. It may surprise you that it's so simple and so inexpensive.

Aloha,

Mark 

Update:

Everything is looking soooo much better than what I saw in the image posted in the OP. No Frogspawn skeleton is showing and the anemone looks like an anemone.

Alk 9.2 dKH, Ca <290 ppm, and Mg 1340 ppm. No need to check N compounds. I can see that everything is fine. The Nitrate test kit must be bad/old. Calcium needs to be dosed heavily and Alk will need to be dosed moderately as the Ca level rises.

We checked SG with a Refractometer and found it to be currently 1.020. It can be raised to 1.025 by topping off with salt water in place of RO water.

The fish are acting normal, eating algae and doing the things that fish do. This tank is headed for the

Aloha,

Mark 

Nope, Nitrates do not create sediment or waste.

That is a healthy sand bed, supporting bugs like Copepods, Amphipods and those little swimmers called Mysid Shrimp. I wouldn't touch it. See the worm tunnels next to the glass.   Lot's of good animals in there doing their cleanup job.

Sounds like bigger rocks are needed to hold the Macro in place in the display. Yes, Damsels eat algae.

FWIW, it's not a fan, it's called a powerhead and the thing that spins to push the water is a propeller.

If there is something creating Nitrates, it is probably where the water drains into the sump. How is that set up? May we see a pic?

May we see a pic of the display as it is now? I would like to see a full frame pic of the left side and another of the right side.

I may be coming your way in the next few days. I'll text to see when we can meet up.

Aloha,

Mark