Adding brightwell alkaline 8.3 to AWC?

JPG Corals · Jan 13, 2026

So i recently purchased an fusion apex jr. As well as a DOS QD doser. Im currently using this to do an AWC. I have it changing 5 gallons of water 24/7 over the course of 7 days on a ~40 gallon tank (Roughly 8% change weekly)

I noticed my Alkalinity is at 6.5dKH (hanna)
I have a bottle of brightwell alkaline 8.3.
Once i reach my target dKH of 8, and I figure out my daily consumption would i be able to to add the brightwell alkaline 8.3 product to my 5 gallon AWC bucket and dose it this way to maintain my ALK?

Any issues with it being mixed over a 7 day period? Will it lose its PH raising abilities? Any other concerns I should be aware of doing it this way?

I figured I'd use this as i have it on hand, but think in the future I will want to try kalk.

Thanks.

Randy Holmes-Farley · Jan 14, 2026

To boost alk by 1.5 dKH over 7 days will need about 0.2 dKH per day.

If your AWC changes 1% daily, that means the AWC water needs to be 20 dKH higher than the tank, and that’s the problem. It will very likely cause a calcium carbonate precipitation event in the new salt water.

You could put it in ATO water.

JPG Corals · Jan 14, 2026

Randy Holmes-Farley said:
To boost alk by 1.5 dKH over 7 days will need about 0.2 dKH per day.

If your AWC changes 1% daily, that means the AWC water needs to be 20 dKH higher than the tank, and that’s the problem. It will very likely cause a calcium carbonate precipitation event in the new salt water.

You could put it in ATO water.

Im not sure if i was unclear, but I wanted to use this in the AWC to maintain the dkh (after I get it to 8.)

I am currently dosing manually at the moment to get it back to 8.

Would this be okay?

Thanks.

Randy Holmes-Farley · Jan 14, 2026

JPG Corals said:
Im not sure if i was unclear, but I wanted to use this in the AWC to maintain the dkh (after I get it to 8.)

I am currently dosing manually at the moment to get it back to 8.

Would this be okay?

Thanks.

Water changes are a poor way to maintain alk.

Depends on how much extra alk you expect to add, but in general, for the reasons I indicated, adding an extra 0.2 dKH to the tank via water change cannot work, which is why folks neither do it nor recommend it.

The best you could do is a naturally high alk salt mix, and hope it doesn’t precipitate before it is used.