Alkalinity and Calcium

Lisa Cain · 2026-10-26T19:25:44-0400

My alkalinity is normally 8-9. I changed 20 gallons of water yesterday and today my calicum was 480 and my alkalinity was 7. Should I go ahead and dose with Brightwell Reef Code B? Or should I give it time? My aquarium is 120 gallons.

tbrown · 2026-10-26T20:03:49-0400

What are you hoping to have your alkalinity at? What does your salt mix at?

Lisa Cain · 2026-10-26T20:05:58-0400

Normally it is around 9. I purchase my saltwater. I can test the saltwater that I purchased to see what the alkalinity is.

tbrown · 2026-10-26T20:10:02-0400

I'd match what your fresh water is so water changes help keep it stable rather than cause swings. If the salt is 9, I'd definitely start looking at dosing to keep it near that. If it's just alkalinity that's lacking, you could consider something as easy as baking soda.

mcarroll · 2026-10-26T21:13:42-0400

Lisa Cain said:
My alkalinity is normally 8-9. I changed 20 gallons of water yesterday and today my calicum was 480 and my alkalinity was 7. Should I go ahead and dose with Brightwell Reef Code B? Or should I give it time? My aquarium is 120 gallons.

Code B is the alkalinity part, correct? That should work.

If you want to dose Code A and B together without running one out first, then making a spot adjustment with baking soda like @tbrown said is a good alternate move.

If you're fine with buying more Code B when you're out, then it's fine to do either one....use what you have IMO.