Alkalinity going up instead of down

[Acros]

I was having this issue as well with instant ocean salt it was mixing at 1.026 salinity and dkh at 16 but I used tap water + instant ocean . ( now use only lfs saltwater as mixing salt creates too much for me , 1600 Mg , 500 Calc and 16 dkh)

I have a 4 stage RODI. I test it regularly with a handheld TDS meter. It is running at 0tds. I wonder if the chaeto is using up phosphates and nitrates, which is contributing to an increase in Alk.

 

[Randy Holmes-Farley Verified Community Expert]

I am seeing Alk rising in my tank. I use a Hanna checker. I added chaeto at the stating of this. I have not seen a lot of growth anyway. My phosphates are at 0.07ppm, Nitrates between 0 and 0.5ppm. I do not have any corals in the tank now (I had a mass dieoff about 2 weeks back). The tank is 3 months old. I do not dose anything. I do 10% water changes every week using instant ocean reef crystals.

Edit: Is it safe to add corals in a week or two? Ph is 8.0

That small alk rise may be from the water changes and lack of demand. Try measuring alk in your new salt water.

 

[Randy Holmes-Farley Verified Community Expert]

I was having this issue as well with instant ocean salt it was mixing at 1.026 salinity and dkh at 16 but I used tap water + instant ocean . ( now use only lfs saltwater as mixing salt creates too much for me , 1600 Mg , 500 Calc and 16 dkh)

Yes, the alkalinity in tap water adds to the alkalinity in the salt mix, potentially creating a very high alk situation.