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What's the ideal calcium level for a mixed reef tank? I've got a 75-gallon with LPS and SPS, running a protein skimmer and dosing two-part. My levels hover around 380 ppm, but some say 420-450 is better. Just wanna make sure I'm not starving my Acroporas.

380 ppm is on the low side for SPS. I keep mine at 420-430, and the growth's been solid. What's your alkalinity sitting at? If it's stable, bumping calcium slowly won't mess with things. Just don't go over 450, or you'll get precipitation issues.

Yo, my tank's chill at 400, but I've only got softies and a couple hammers. Dunno if it's worth tweaking for your setup, but my dude at the LFS swears by 420 for SPS. Maybe cut it halfway and see how they vibe?

DuskRaven7 wrote: ↑Fri Jul 18, 2025 2:17 am Yo, my tank's chill at 400, but I've only got softies and a couple hammers. Dunno if it's worth tweaking for your setup, but my dude at the LFS swears by 420 for SPS. Maybe cut it halfway and see how they vibe?

Softies are less picky, but Acros need that extra calcium. Finley11, what's your magnesium at? Low mag can throw off calcium uptake even if the numbers look good.

My tank's small, 30 gallons, but I keep calcium at 410. Corals seem happy. How often you testing? I do it weekly, sometimes twice if I'm tweaking stuff.

ripple_under wrote: ↑Fri Jul 18, 2025 1:31 am 380 ppm is on the low side for SPS. I keep mine at 420-430, and the growth's been solid. What's your alkalinity sitting at? If it's stable, bumping calcium slowly won't mess with things. Just don't go over 450, or you'll get precipitation issues.

Alkalinity's at 8.5 dKH, mag around 1350. Sounds like I should nudge calcium up. Gonna try raising it 10 ppm per day and monitor polyp extension.

That's a solid plan. Your alk and mag are in a good spot, so the calcium bump should work. Watch for any tissue recession on the Acros, though. Had that happen once when I overshot.

Aight, good luck with the tweaks. My torch would throw a fit if I messed with params that much, but SPS are drama queens anyway.

Keep us posted, Finley11. I'm curious if the slower ramp-up avoids stress. Last time I adjusted too fast, my Montipora bleached for a week.

My test kit's kinda sketchy, so I double-check with the LFS. Maybe try that if things look off?