Randy, I am having trouble with about 40% of my acropora's, the colors have slowly faded in the past three months, the skin looks thin, recently the polyps are retracted and some have no growth in the past 7 months. Battle Corals Banana Caroliniana February 27, 2017 September 9, 2017 ATL Shades of Fall February 27, 2017 September 9, 2017 I sent a water sample from August 21st to ATI ICP and the results are below. Tank Specs: 120 Gallon reef ready Perfecto Glass Aquarium (48”x24”x24”) 30 gallon breeder sump/small refugium with chaetomorpha algae (36”x12”x16”) Water Movement Equipment One Jebao DCT-6000 Pump (1,056 - 1,585 GPH, 42 watts) Two Jebao PP-15 Powerhead (317-3,962 GPH, 12-35 watts) Loc-Line return hose (0.75”) Lighting Equipment Two Lumenarc III mini Stealth Pendants (14.5”x14.5”x7”) Two 250 watt 20K Hamilton DE Metal Halide Bulbs (8 hour light cycle) Two 250 watt LuXcore Dimmable Electronic Ballast One LET Miro-4 retrofit T-5 48” lighting 2x54watt (12 hour light cycle) Two ATI Actinic 54 watt T-5 Bulb Two SB Reef Lights Actinic LED Light Bar (7 hour light cycle) Water Quality Equipment Neptune Apex Aquacontroller Gold (pH, ORP, Temperature & Conductivity) 6 Stage Bulk Reef Supply Reverse Osmosis with Two DI Filters (75 GPD) & booster pump SKIMZ SM-163 Protein Skimmer (19 watts) AutoAqua Smart ATO Micro Auto Top Off System Jebao Stand Alone Dosing System (4 Pump) Two Eheim Jager 150 watt Heater (13”) One Eheim Jager 200 watt Heater (15”) 100 lbs. of Live Rock (Fiji, Tonga Fusion, Kaelini & Pukani) Chaetomorpha algae Additives Aquaforest Reef Salt Mix Calcium Chloride (Randy's Two-Part) BRS Soda Ash (Alkalinity Buffer) (Randy's Two-Part) Mag Pellet (Magnesium Chloride) (Randy's Two-Part) CVS Epsom Salt (Magnesium Sulfate) (Randy's Two-Part) Potassium Chloride when needed Seachem Strontium Chloride when needed Seachem Reef Trace when needed Seachem Reef Plus when needed Seachem Flourish Phosphorous when needed Seachem Flourish Iron when needed Kent Marine Lugol’s Iodide when needed Bulk Reef Supply ROX 0.8 Activated Carbon ran in a mesh media bag 18 Fish 1 Geometric Pygmy Hawk (Plectranthias inermis) 1 McCosker’s Flasher Wrasse (Male) (Paracheilinus mccoskeri) 1 Melanurus Wrasse (Halichoeres melanurus) 1 Mystery Wrasse (Pseudoceilinus ocellatus) 1 Chevron Tang (Ctenochaetus hawaiiensis) 1 Yellow Tang (Zebrasoma flaviscens) 1 Desjardini Sailfin Tang (Zebrasoma desjardini) 1 Blue Eyed Tang (Ctenochaetus binotatus) 1 Tail Spot Blenny (Ecsenius stigmatura) 2 Talbot’s Damsel (Chrysiptera talboti) 1 Royal Gramma (Gramma loreto) 4 Azure Damsel (Chrysiptera hemicyanea) 2 Springer’s Damsel (Chrysiptera springeri) Inverts 1 Scarlett Skunk Cleaner Shrimp (Lysmata amboinesis) 4 Pincushion Urchins Nitrates were around 25 to 50 ppm according to Salifert so I was dosing vinegar to lower my nitrates. ICP shows 19 ppm my latest Salifert test shows 10 ppm. Could dropping my nitrates from such a high value within a month to a month and a half period cause the polyps to retract? One thought is I added the LED strips in March, now that we are in the summer and longer daylight hours maybe the corals were overexposed with light as my tank is next to two windows. During the winter months the colors look better during the shorter sunlight periods. Also, the tank is bare bottom. I feed mostly pellet food, could that be starving my corals?