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My SPS corals have been looking a bit pale lately, and I suspect my magnesium levels might be off. I've been testing with Salifert kits, but I'm not sure how much to dose. My tank is a 75-gallon mixed reef with a Red Sea Reefer skimmer, running T5 and LED hybrid lighting. Parameters are stable at 8.2 dKH, 420 calcium, but magnesium is at 1200. Should I bump it up to 1300?

1200 is definitely on the low side for a reef tank. I'd aim for 1350-1400, especially with SPS. I use Brightwell Magnesion-P, dosing 50ml daily in my 120-gallon until I hit target, then maintain with weekly doses. What salt mix are you using? Some brands run low on mag out of the box.

Yo, same issue here last month. My acros were bleaching at 1250 mag. Upped it to 1350 over a week with ESV B-Ionic, now they're coloring up nice. Just go slow, like 50ppm per day max. What's your salinity at? Low salinity can mess with mag uptake.

creekflow wrote: ↑Mon Jun 16, 2025 5:40 am Yo, same issue here last month. My acros were bleaching at 1250 mag. Upped it to 1350 over a week with ESV B-Ionic, now they're coloring up nice. Just go slow, like 50ppm per day max. What's your salinity at? Low salinity can mess with mag uptake.

Solid advice. I'd also check your potassium levels—low K can mimic mag deficiency. Running ICP tests monthly saved me from chasing ghosts last year.

My LFS told me mag doesn't matter much unless you're keeping sticks. Is that true? I've got softies and LPS in a 40-gallon with mag at 1100 and they seem fine. Using Instant Ocean salt, weekly 10% changes.

Nah, mag matters for all corals—it's part of the calcification process. Softies might tolerate lower levels, but why risk it? I'd bump yours to at least 1250. IO is notorious for low mag, switch to Reef Crystals or mix your own supplements.

Pro tip: dose mag at night if you're using two-part. Daytime dosing can cause precipitation in high-pH tanks. Lost a bottle of expensive trace elements that way before I figured it out. Now I dose mag at midnight with a Kamoer pump.

florinx wrote: ↑Mon Jun 16, 2025 6:10 am My LFS told me mag doesn't matter much unless you're keeping sticks. Is that true? I've got softies and LPS in a 40-gallon with mag at 1100 and they seem fine. Using Instant Ocean salt, weekly 10% changes.

Your LFS is giving sketchy advice. Even mushrooms and zoas need proper mag for skeletal support. At 1100, you're flirting with osmotic stress. Try raising it slowly over two weeks.

Anyone tried the DIY magnesium mix with Epsom salt and magnesium chloride? Way cheaper than branded products. I've been using the BRS recipe in my 180-gallon SPS dominant system for years. Just gotta watch the sulfate buildup if you're heavy on the Epsom.

Thanks for all the input. I'll start dosing slowly to reach 1350 and monitor the SPS response. Appreciate the salt mix tips too—might switch to Reef Crystals after this bucket runs out.