alkalinity for SPS dominance

[darkprowl]

My SPS corals aren't thriving like they used to. I've been keeping alk stable at 8.5 dKH, but growth is slow. Anyone else run into this? Tank's a 75g with Radion lights, running a Reef Octopus skimmer. Parameters are 0 ammonia, 0 nitrite, 5 nitrate, 420 calcium. Weekly 10% water changes with Red Sea Coral Pro.

[landfall]

8.5 dKH is solid, but SPS can be picky. What's your magnesium at? I've found keeping it around 1350-1400 helps. Also, how old are your bulbs? Radions lose intensity after 9-12 months. My Acros took off when I bumped alk to 9 and swapped bulbs.

[fluxonix]

8.5 dKH is solid, but SPS can be picky. What's your magnesium at? I've found keeping it around 1350-1400 helps. Also, how old are your bulbs? Radions lose intensity after 9-12 months. My Acros took off when I bumped alk to 9 and swapped bulbs.

Yep, mag's key. I run mine at 1380, alk at 9.2. Darkprowl, you dosing anything besides water changes? Two-part or kalk?

[Freshstar]

My tank's smaller (40g), but I had the same slump. Upped alk to 9.5 and growth exploded. Might be worth a slow creep up. Also, what's your flow like? SPS dig random chaotic movement—I added a Nero 5 and they perked right up.

[rotorblade]

Flow's huge. My Montis were meh until I pointed a Gyre at 'em. Darkprowl, you running carbon or GFO? Sometimes stripping too much can mess with trace elements. I cut back to half-dose and saw better polyp extension.

[tigerly]

Not to hijack, but how often are you all testing alk? I'm new to SPS and paranoid about swings. Testing daily feels overkill, but my LFS said weekly might miss dips.

[ramblo]

Not to hijack, but how often are you all testing alk? I'm new to SPS and paranoid about swings. Testing daily feels overkill, but my LFS said weekly might miss dips.

Daily for the first month, then dial it back. Once you know your tank's consumption rate, 2-3x/week is chill. I use a Hanna checker—way faster than kits.

[darkprowl]

Thanks for the tips, all. Mag's at 1300, so I'll bump that. Bulbs are 10 months old… might be time. Running a MP40 on reef crest mode, but I'll tweak the flow. Dosing Two-Part daily, alk's pretty steady. Gonna test mag more often.

[mintyke]

Don't sleep on potassium either. My Stags browned out until I realized K+ was at 350. Brought it to 400 and colors popped. Salifert makes a decent test kit for it.

[lighton7]

Consistency beats chasing numbers. I keep alk at 8.8, cal 440, mag 1350. Dosing pumps on timers to avoid swings. SPS hate surprises more than imperfect params.