Shrinking soft corals

i have a 40 gal Acrylic tank which is actually 2-20gal towers connected by 2 6" tubes. For the past 3 months, I have slowly been losing my soft corals. The mushrooms, button polyps, and zoanthids are all okay. I lost my golden hammer, and clove polyps completely. My green hammer was doing well until a week ago. The trumpet coral is beginning to close up and is losing color. Water tests are pH 8.1, Nitrates 20, Nitrites 0, Alkalinity 10 dKH, Calcium 470 ppm, Salinity 1.024, Temp 78.2, Magnesium 1200 ppm, Ammonia 0, Phosphate 0.008. I am not adding anything for calcium, as it is a tad high. I feed Rotifers 2x/week and Mysis shrimp 5x/wk. Fish include a pair of black ice Ocellaris, a pair of PJ Cardinals, A coral beauty, a chalk basslet, pair of neon gobys, pair of fire Shrmp, pair of cleaner shrimp. The tank has been up and running for 3 years. When the corals first started to die off, we saw our Atlantic Pygmy angel picking at them so sold him. We have looked at night and have not found anything else picking at them.

A month ago, our Salinity had went down to 1.022 so took a week to gradually bring it back up to 1.024-5. Lighting is with Fluval Marine LEDS. We have 2 Fluval Powerheads running that were rated for a tank 3 times the size of ours. We are running 2 Fluval 306 canister filters and a Fluval Protein Skimmer. We do 10-15% water changes every 10 days to 2 weeks.

Does anyone have any advice or ideas as to why the corals are not doing well.

 

I would keep an eye on the coral beauty. Angels are not the best idea in a reef tank but yet doable.
Color loss comes from alk swing, do you have an ato?

 

Coral beauty has not been seen near the corals, including day and night that we can tell. Have checked many times.

 

I wish I had seen this sooner. when corals get sick there are usually 3 things. FLOW, 'TRATES AND LIGHT! I would be surprised if the problem is not one of these three things

Your nitrates are too high. Your Phosphates are okay but your test must be accurate. DID YOU CHANGE LIGHT WHEN THE PROBLEM BEGAN?


ALSO, my corals always look better after I do a 50% water change.

 

The hammer coral has been in the tank for over a year without any problems. We have not changed flow or lighting. I will do a large water change tomorrow and make sure all the lights are working properly.

 

How old are your bulbs? Old, dimming bulbs can substantially affect corals! MH bulbs can dim a lot after 10 months. Also, suggest you test for unwanted copper.

If that hammer was fine for a year then got sick then SOMETHING changed.

 

Testing the water is the first thing i would do. Never a bad idea to do a water change but knowing if a level is low would best get them back to life.