Who Gives A Fish Forums

I've been struggling to keep my SPS happy lately. My magnesium levels are sitting around 1200 ppm, but I've heard conflicting advice on the ideal range. What's everyone else running for their SPS tanks?

1200 is kinda low, dude. I keep mine at 1350, and my Acros are poppin'. You gotta bump it up slow though, like 50 ppm per day.

I've had success with 1300–1350 ppm. Anything lower and my montis start looking pale. What's your calcium and alk at? They all play together.

My tank's been thriving at 1280 ppm. Not too high, not too low. Just gotta find that sweet spot for your system.

rubyking wrote: ↑Sun Jul 20, 2025 11:59 am I've had success with 1300–1350 ppm. Anything lower and my montis start looking pale. What's your calcium and alk at? They all play together.

Yep, alk's gotta be stable too. If that's swinging, mag won't matter much.

I aim for 1300 ppm. My SPS seem to do best there. How often are you testing? Could be a consistency issue.

I'm new to SPS, but my LFS said to keep mag at 1250. Is that too low?

1250 might work, but it's on the lower end. If your corals are happy, roll with it. If not, creep it up.

I run mine at 1350 ppm, and my SPS are growing like weeds. But like others said, stability is key. No point in chasing numbers if everything else is out of whack.

1200 is sketchy for SPS, bro. Bump it to 1300 and see how they react. My tank went from meh to wow after adjusting mag.