Can't raise alkalinity...

NigeltheBold · Dec 21, 2019

I'm new to reef keeping. I've had marine fish for years, but I'm just now getting into corals and reef chemistry. I'm having a strange problem. I used RO water and Reef Crystals to start my tank several months ago, and I use RO water for top-ups and with reef crystals for water changes. I have a couple of sps frags, a 3-4" cauliflower Coral, a very healthy brain Coral frag, and a new Maxima clam. Calcium is under control (I keep it between about 420 and 450ppm). Magnesium is super high, around 1800 ppm and it hasn't gone down much since I started the tank. I can't seem to get the alkalinity above 7.5 dKH, even after adding the maximum daily dose of red Sea additive several days in a row. I also tried Brightwell Liquid Reef, which is supposed to raise both calcium and alkalinity, but it only seemed to raise the calcium. What am I doing wrong? Is this related to the magnesium levels being high?

Randy Holmes-Farley · Dec 21, 2019

Liquid Reef is not useful. Put it way back on a shelf and forget it. It’s absurd they continue to sell aragonite . It’s just fine sand. It won’t dissolve.

how much alk in dKH per day are you adding with the Red Sea alk additive? That’s the way to know what you should be seeing.

NigeltheBold · Dec 22, 2019

Randy Holmes-Farley said:
Liquid Reef is not useful. Put it way back on a shelf and forget it. It’s absurd they continue to sell aragonite . It’s just fine sand. It won’t dissolve.

how much alk in dKH per day are you adding with the Red Sea alk additive? That’s the way to know what you should be seeing.

Over the past few months, I've gone through an entire bottle of the Red Sea alkalinity supplement. I added no more than 15mL per day. I don't have the bottle, so I don't know exactly what that equates to (there was a chart on the back) in dKH per day, but it was under the maximum daily limit. I believe I was targeting about 1 dKH per day. But it just kept dropping... it started around 10.5 and dropped down to about 7.5, despite my additions of the supplement. Meanwhile, Magnesium has never been below 1700ppm and Calcium has never been below about 415ppm.

Randy Holmes-Farley · Dec 22, 2019

Maximum daily limit really means nothing. It is designed for folks who do not measure alk to not overdose think more is better.

1dKH per day is not very much.

NigeltheBold · Dec 23, 2019

Randy Holmes-Farley said:
Maximum daily limit really means nothing. It is designed for folks who do not measure alk to not overdose think more is better.

1dKH per day is not very much.

Oh, I thought the limit was there to prevent stress on corals. I read that large swings like that can be harmful. What's the biggest increase you'd allow in a 24 hour period?

Randy Holmes-Farley · Dec 23, 2019

NigeltheBold said:
Oh, I thought the limit was there to prevent stress on corals. I read that large swings like that can be harmful. What's the biggest increase you'd allow in a 24 hour period?

You do not want big swings if you have sps, but that's not where a daily limit comes from. If corals consume 4 dKH per day, you will need to dose 4 dKH per day. But the recommended limit is likely lower, again, for folks not measuring.

If the needed daily dose is more than 0.5 dKH, I'd split it up into multiple doses, or use a dosing pump to spread over many dosing events.

NigeltheBold · Dec 23, 2019

Randy Holmes-Farley said:
You do not want big swings if you have sps, but that's not where a daily limit comes from. If corals consume 4 dKH per day, you will need to dose 4 dKH per day. But the recommended limit is likely lower, again, for folks not measuring.

If the needed daily dose is more than 0.5 dKH, I'd split it up into multiple doses, or use a dosing pump to spread over many dosing events.

Okay, I'll give it a shot. Thanks for the help!