Why Alk is still so low?

[WallysWorld]

I can't get my Alk back to more normal levels of 7-8 dKH. It currently measures at 4.1 dKH and I've validated my measurement methods by testing new fresh salt water. Tests of new salt water matches parameters specified by salt manufacturer. I'm highly confident in my test results, but never say never...

Any thoughts on why Alk is still so low, and should I be doing something in addition to double dosing Foundation B (KH/Alk) and large water changes?

Background and parameters:

I had a mistake where I was double dosing Ca+ (Red Sea Foundation A) and not dosing KH/Alk (Red Sea Foundation B) for about 4-5 weeks. Mistake was discovered 3 weeks ago, and since then I have stopped dosing Ca+ entirely. I'm double dosing the Alk/KH (Foundation B) from previous stable amounts, 25 ml/day, and I've done large water changes weekly, about 20% each time (three in total). New water has Alk of 7.7 dKH when freshly mixed. I test Alk a day after the water change and its been running at about 4 dKH.

Temp - 77.9°F
Salinity - 35 ppt
pH - 7.8
Alk - 4.1 dKH
Calcium - 490 ppm
Mg - 1500 ppm
Nitrate - 4 ppm
Phosphate - 0.06 ppm
Volume 37 gallons

Daily dosing:
Foundation B (KH/Alk) - 25 ml
Foundation A (Ca+) - 0.0 ml
Foundation C (Mg) - 1 ml
NO_POx - 4 ml

 

[Randy Holmes-Farley Verified Community Expert]

That's more than 4 dKH per day. Should be plenty unless lots of precipitation is taking place.

maybe try baking soda instead to have a lower pH and less likelihood of precipitation.

Maybe something is wrong with the additive, or the kit. Maybe try dosing the new salt water by 1 dKH and see if you get the expected rise.

FWIW, the Red Sea product is not designed for 1:1 dosing, so don't assume that's a good starting point for stability as it is with most two part systems.

 

[crazywegian]

Tank size and inhabitants?

 

[WallysWorld]

Tank size and inhabitants?

Its a Reefer 170 (~37 gallons). One clown, one blenny, one purple firefish, several hermits and snails. Lots of LPS coral