Who Gives A Fish Forums

I've noticed my Acropora and Montipora are losing their vibrant colors. My tank is a 75-gallon mixed reef with Radion XR15 lights, running at 60% intensity for 10 hours. Parameters are stable: 8.1 pH, 1.025 salinity, 0 nitrates, 0 phosphates, 420 calcium, 1300 magnesium. Any ideas what's causing this?

Yo, sounds like your nutrients are too low. SPS need some nitrates and phosphates to keep their colors poppin'. Try bumping nitrates to 5 ppm and phosphates to 0.03 ppm. Also, check your alk, bro. If it's swinging, that'll mess with your corals big time.

I agree with reefkeeper1. Low nutrients can bleach SPS. I'd also look at your lighting. Radions are strong, and 60% might be too much if your corals are high up. Try reducing intensity to 50% or raising the lights a bit. How's your flow? Acros need random, turbulent flow to thrive.

reefkeeper1 wrote: ↑Sat Apr 19, 2025 6:51 am Yo, sounds like your nutrients are too low. SPS need some nitrates and phosphates to keep their colors poppin'. Try bumping nitrates to 5 ppm and phosphates to 0.03 ppm. Also, check your alk, bro. If it's swinging, that'll mess with your corals big time.

Exactly this. Alk swings are a silent killer. What's your dKH? If it's not between 8-9, you're gonna stress your corals. Also, how old are your bulbs? Older LEDs lose spectrum over time.

My SPS did the same thing when I switched salts. Are you using the same brand? Some salts have trace elements that SPS love. Also, how often are you feeding? Corals need amino acids and vitamins to keep their colors. I dose Acropower twice a week and see a huge difference.

Thanks for the advice, everyone. I'll try raising nitrates slightly and check my alk stability. My dKH is at 8.5, but I'll monitor it more closely. Lights are about a year old, so maybe it's time for a spectrum check.

Don't forget about trace elements! Iodine, strontium, and potassium are huge for color. Test for those if you can. Also, how's your temp stability? Fluctuations over 1-2 degrees can stress SPS. My tank dropped to 76 last winter, and my Acros browned out for weeks.

I had this issue when my RO/DI filters were spent. TDS creep can introduce contaminants that affect coral color. When was the last time you changed your filters? Also, any new tankmates? Some fish nip at corals, causing stress.

fishdish wrote: ↑Sat Apr 19, 2025 12:47 pm My SPS did the same thing when I switched salts. Are you using the same brand? Some salts have trace elements that SPS love. Also, how often are you feeding? Corals need amino acids and vitamins to keep their colors. I dose Acropower twice a week and see a huge difference.

Yep, salt mix matters. I switched to Red Sea Blue Bucket and my colors came back in a month. Also, +1 on amino acids. They're a game-changer.

Lol, my SPS look like crap no matter what I do. Maybe I should just stick to softies. But hey, at least my clownfish are happy. Good luck, OP!