loss of alkalinity?

[no_Wedge]

for some reason my alkalinity quickly depletes. I have a 24g aquapod with quite a bit of sps in it. (maybe this is why?) I do 10-15% water changes weekly with coral pro salt high levels of alkalinity and magnesium.
I have to dose almost daily with seachem reef builder since within two days it drops from 8dkh to 7or less.
Is this just due to the concentration of sps corals and is the only way to fix this by supplementing daily?

[Percula9]

What is the calcium and magnesium levels?

[no_Wedge]

the new water is alkalinity 12dkh calcium 450ppm and magnesium 1320, the tank sits around 420calcium alkalinity drops quickly and i don't have a test kit for mag.
also there is macro algae for nutrient absorption could this lower alkalinity?

[bertoni]

Many tanks require daily supplementation. A 2-part is a good way to get started. That's keep both calcium and alkalinity in the acceptable range. Corals consume 2.8 dKH for each 20 ppm calcium, so calcium doesn't seem to change rapidly.

[no_Wedge]

the new water is alkalinity 12dkh calcium 450ppm and magnesium 1320, the tank sits around 420calcium alkalinity drops quickly and i don't have a test kit for mag.
also there is macro algae for nutrient absorption could this lower alkalinity?

[bertoni]

No, macroalgae don't consume alkalinity, unless they're a calcareous alga, like Halimeda.

[no_Wedge]

hmm ok i may also use baking soda to raise my ph a little seems a bit low at around 7.8 at it's low and little over 8 at it's high.

[Percula9]

The sps must be consuming it for growth. Just add a little every day to keep up with the demand. Sps doesn't like high alk any way.

[bertoni]

Baking soda is a good alkalinity supplement, but it has a slight lowering effect on pH in a saltwater tank, when first added. After the carbon dioxide from it outgasses, the pH will rise a little bit, but not much. I think 7.8 is fine for pH, but a lime drip could raise it some.

[no_Wedge]

well i went with some baking soda baked to make it sodium Carbonate, which raises ph since my ph was a little down. works great, and just a 1/4 of a teaspoon raised ph about .2