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My Acropora tenuis isn't looking too hot lately. The polyps are retracted, and the color's faded. Running a 75-gallon tank with Radion XR15 lights, 8 hours a day. Parameters are 78F, 1.025 salinity, 8 dKH, 420 calcium, 1350 magnesium. Any ideas what's messing with it?

How old's your tank? Acropora tenuis can be picky about stability. If it's under a year, they might just need more time to settle. Also, what's your phosphate level? Even a tiny spike can stress them out.

I've had similar issues before. Check your flow—too much direct current can piss them off. I run two MP40s at 30% on opposite sides, and mine perked up after adjusting.

tawnie wrote: ↑Sat Jul 12, 2025 7:39 pm I've had similar issues before. Check your flow—too much direct current can piss them off. I run two MP40s at 30% on opposite sides, and mine perked up after adjusting.

Yep, flow's huge. I dialed mine back and saw way better extension. Also, what's your nitrate sitting at? These guys hate it too clean.

Mine did the same thing when I switched salts. You using the same brand as always? Sometimes they're just drama queens about changes.

Lighting could be part of it. XR15s are strong—you might need to raise them or shorten the photoperiod. I run mine at 6 hours peak intensity, 12 total with ramp-up. Also, how often are you feeding? They need amino acids regularly.

Agree with Bamda on feeding. I dose amino acids twice a week and spot-feed reef roids. The polyps extend way more after. What's your alk stability like? Daily swings over 0.5 dKH can stress them.

Thanks for the tips, everyone. Gonna tweak the flow first and check my phosphate kit—it's kinda old. Appreciate the help!

dWright wrote: ↑Sun Jul 13, 2025 12:17 am Thanks for the tips, everyone. Gonna tweak the flow first and check my phosphate kit—it's kinda old. Appreciate the help!

Good call on the kit. Bad test kits cause so many headaches. Let us know how it goes.

One more thing—if you're running carbon, swap it out. Old carbon can leach junk back into the water. Happened to me last year.