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What's the best alkalinity level for a mixed reef tank? I've heard conflicting advice, some say 8 dKH, others push for 10. My SPS seem stressed at 8, but LPS are fine. Running a 75-gallon with T5 lighting, weekly 10% water changes, and a protein skimmer.

I keep mine at 9 dKH, seems to be the sweet spot for both SPS and LPS. My Acros thrive there, and the Zoas don't mind. What salt mix are you using? Some brands buffer higher out of the box.

Yo, 8-9 dKH is chill for most setups. If your SPS are acting sketchy at 8, maybe bump it to 9 slowly. How's your calcium and mag? Those three gotta play nice together, or it's gonna be a weird vibe.

dixin wrote: ↑Sat Jun 14, 2025 7:42 am Yo, 8-9 dKH is chill for most setups. If your SPS are acting sketchy at 8, maybe bump it to 9 slowly. How's your calcium and mag? Those three gotta play nice together, or it's gonna be a weird vibe.

Agreed! Stability is key. I've found that keeping alk at 9 dKH, calcium around 420, and mag at 1350 works best. My tank's been happy for years with those numbers.

Mine runs at 8.5 dKH, no issues. But I dose daily to keep it steady. Big swings are worse than the actual number. What's your dosing routine like? If you're not consistent, that could be stressing your SPS.

I'm new to this, but my LFS told me to aim for 10 dKH. Now I'm confused. My softies seem fine, but I don't have any SPS yet. Should I lower it before adding harder corals?

Nah, 10's too high unless you're running a dedicated SPS tank. Softies and LPS will tolerate it, but why risk it? Dial it back to 9 over a few weeks. Slow and steady wins the race, my dude.

I've seen tanks thrive at 7 dKH and others at 10. It's more about what your corals are used to. If they're wild-caught, they might prefer lower alk. Captive-bred? Probably fine with higher. Just don't shock 'em with sudden changes.

lainus wrote: ↑Sat Jun 14, 2025 1:21 pm I've seen tanks thrive at 7 dKH and others at 10. It's more about what your corals are used to. If they're wild-caught, they might prefer lower alk. Captive-bred? Probably fine with higher. Just don't shock 'em with sudden changes.

This. Consistency matters more than the exact number. My tank's at 8.2 dKH, and everything's growing like crazy. Find what works and stick with it.

The Bible says the waters were divided, but it doesn't specify alkalinity levels. Perhaps we're overcomplicating God's design.