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my coral is bleaching, why?
Posted: Thu Jul 31, 2025 1:24 pm
by voyen
My coral is bleaching and I don't know why. The tank is a 40 gallon with T5 lighting, running for about 8 months. Parameters are 78°F, salinity 1.025, nitrates 5 ppm. I do weekly 10% water changes with Red Sea salt. Any ideas?
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 1:55 pm
by koolkid
Bleaching can happen if the light's too intense. How long are your T5s on each day? Also, what's your phosphate level? High phosphates can stress them out.
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 3:52 pm
by aquabreed
I had the same issue last year. Turns out my heater was sketchy, causing temp swings. Check if your heater's consistent. Also, what coral species is it? Some are more sensitive than others.
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 4:28 pm
by Nellie
voyen wrote: ↑Thu Jul 31, 2025 1:24 pm
My coral is bleaching and I don't know why. The tank is a 40 gallon with T5 lighting, running for about 8 months. Parameters are 78°F, salinity 1.025, nitrates 5 ppm. I do weekly 10% water changes with Red Sea salt. Any ideas?
Your nitrates are fine, but what about alkalinity and calcium? If those are off, it can cause stress. Test kits for those are a must.
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 4:56 pm
by SlateFang
Yo, could be the flow too. If the coral's in a dead spot, it's gonna struggle. What's your powerhead situation? Also, any new fish messing with it?
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 6:25 pm
by mikoson
I agree with checking alkalinity and calcium. Also, how old are your T5 bulbs? They lose intensity over time. If they're older than 12 months, it's time to replace them.
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 7:15 pm
by luxion
Bleaching's often a light issue. Are your T5s on a ramp schedule or just full blast? Sudden changes in intensity can shock them. Gradual adjustments are better.
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 8:11 pm
by voyen
Thanks for the tips, everyone. I'll test alkalinity and calcium today. The bulbs are about 10 months old, so maybe that's part of it. Flow seems good, but I'll double-check.
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 9:04 pm
by koolkid
voyen wrote: ↑Thu Jul 31, 2025 8:11 pm
Thanks for the tips, everyone. I'll test alkalinity and calcium today. The bulbs are about 10 months old, so maybe that's part of it. Flow seems good, but I'll double-check.
Cool, let us know what the tests say. Also, if you're gonna replace the bulbs, do it one at a time to avoid shocking the tank.
Re: my coral is bleaching, why?
Posted: Thu Jul 31, 2025 10:53 pm
by aquabreed
Yeah, and keep an eye on the coral's response. If it starts to recover, you'll know you're on the right track. Patience is key here.