Alkalinity rapidly dropping. Any thoughts?

[Sordfish]

Up until 5 days ago I was using Red Sea coral pro salt along with daily 31 ml of all-for-reef. I set up a Kamoer auto water change 5 days ago to do 2.5% daily water changes. I changed the salt to tropic Marin coral pro salt since my testing over the last few months showed that Red Sea Coral pro is not a stable salt over the course of days (despite what BRSTV said, I found the alkalinity of the freshly mixed salt dropped from around 10dkh to 6dkh over the course of 4 to 5 days. I tried all permutations of heater/no heater, pump/no pump in anticipation of daily water changes and saw little difference in the degradation).

Red sea coral pro mixed at 10dkh. My tank was rock solid at 9dkh for months. Now that I started 2.5% daily water changes with the tropic Marin coral pro salt (which mixes at 7.6dkh) my alkalinity dropped to 8.1 in 5 days. That seems like an inordinate amount of drop for what is effectively a 10% water change. I did not alter all-for-reef dosing, and nothing else changed in the tank.

Any thoughts as to what may be causing this drop? The tank is about 6 months old and kept at a temp of 77-78. Ph was between 8.0-8.2 but now is between 7.9-8.1. The ph variations are between morning and night.

Thanks in advance for your input.

Edit: it looks like my doses developed an air leak. I’ll correct that and hopefully it’ll resolve the issue.

 

[Randy Holmes-Farley]

Let us know if that doesn’t solve the issue.

 

[bushdoc]

Edit: it looks like my doses developed an air leak. I’ll correct that and hopefully it’ll resolve the issue.

That or blocked line- been there, seen it too.

 

[Sordfish]

That or blocked line- been there, seen it too.

I checked for a blocked line. It doses, but 90%air.

It also shows the importance of regular testing. Thanks to adding the water changer I was testing daily. If not for that I test once every few weeks. With that routine I would have had a crash of my SPS, for sure. Time to start saving for a Trident - I know myself well enough to know I’ll not maintain daily testing.

 

[bushdoc]

I would recommend testing alkalinity at least twice a week.I was doing it weekly, initially, but switched to twice a week.
Trident, yes, good idea, but with proper vigilance you can do without it.