Hi alk demand!

[Rodrigo_BG]

My tank consume 3 times more alk than ca, is that normal? Why it could be happening?

[bertoni]

I'm not sure what you mean. Are you dosing a 2-part?

[Rodrigo_BG]

yes I'm dosing 2-part.

look, last week I tested my alk double checking with two test brands and it was 6dKH. So I past 2 days dosing BS to climb it to 9dKH. Today (1 week later) I tested it again and guess what? 6dkH again! Now I'm dosing 50ml/day of ca against 150ml/day of BS to stop falling.

[bertoni]

I suspect the tank needs the extra calcium, unless the salt you're using is high in calcium. How big is the tank? 50 ml isn't a large dose for a larger (60-90g) system.

[Rodrigo_BG]

Jonathan my tank is lacking for alk and you think I should dose more ca is that right?

my ca is at 400 in a 65g tank.

[bertoni]

If you don't dose the calcium, over time it'll drop. It appears to drop much more slowly than alkalinity because there's so much more of it in seawater than alkalinity, in terms of consumption rates. As long as you're happy with the calcium level, and willing to measure regularly, you may dose it as you want.

That level of dosing is high for that size system. Have you checked the magnesium level? Low magnesium can increase the alkalinity consumption rate of a tank, although it's very rare.

[Rodrigo_BG]

yes my mg seems to be always low.. 1000/1100 with elos.

[bertoni]

Typically, 1100 ppm is enough to avoid trouble, but I'd try bumping it up to 1285 ppm or so, which will take a lot of supplement. I'd also get a second opinion on the alkalinity test kit, just in case, but I probably wouldn't worry much, otherwise.