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My corals aren't growing as fast as they used to. I've been testing calcium levels, and they're sitting around 380 ppm. Tank's a 75-gallon mixed reef with T5 lighting, running a protein skimmer. Should I bump it up to 420 ppm, or is there something else I'm missing?

380 ppm's a bit low for most SPS, gonna wanna aim for 420-450 ppm. What's your alkalinity at? If it's outta whack, no amount of calcium's gonna help. Also, check your magnesium, should be around 1300-1350 ppm to keep things stable.

I've got the same issue in my 40-gallon. My calcium's at 390 ppm, but my zoas and mushrooms seem fine. Do soft corals even care about calcium levels? I'm using Red Sea salt, weekly 10% water changes.

dalerose wrote: ↑Wed May 21, 2025 10:28 pm 380 ppm's a bit low for most SPS, gonna wanna aim for 420-450 ppm. What's your alkalinity at? If it's outta whack, no amount of calcium's gonna help. Also, check your magnesium, should be around 1300-1350 ppm to keep things stable.

Yep, magnesium's key. I had a similar problem last year, and balancing Mg fixed it. Folkster, what salt mix are you using?

Thanks for the tips. I'm using Instant Ocean Reef Crystals. Alkalinity's at 8 dKH, magnesium is 1250 ppm. Guess I'll start with raising Mg first.

Soft corals like zoas don't need much calcium, but LPS and SPS do. Sweetie_22, if you're sticking with softies, you're probably good. Folkster, how often are you dosing? Daily or weekly?

I'd recommend a two-part dosing system if you're not already using one. Keeps things steady. Also, what's your pH like? Low pH can mess with calcium uptake.

Jumper wrote: ↑Thu May 22, 2025 4:57 am I'd recommend a two-part dosing system if you're not already using one. Keeps things steady. Also, what's your pH like? Low pH can mess with calcium uptake.

Totally agree. I switched to a doser last year, and my Acroporas have never looked better. Folkster, are you running a refugium? Macroalgae can help stabilize params.

My tank's a 55-gallon with mostly LPS. Calcium's at 400 ppm, alk at 9 dKH. Everything's happy, but I'm curious if I should push calcium higher for faster growth.

wavekeeper wrote: ↑Thu May 22, 2025 6:56 am My tank's a 55-gallon with mostly LPS. Calcium's at 400 ppm, alk at 9 dKH. Everything's happy, but I'm curious if I should push calcium higher for faster growth.

If it ain't broke, don't fix it. LPS don't need crazy high calcium like SPS. Focus on stability over chasing numbers.