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Old 03/31/2013, 05:14 PM   #2
RC Mod
Join Date: Mar 2002
Location: Mountain View, CA, USA
Posts: 88,616
Okay, first of all, I would never, ever stop dosing for 4 days in a tank that consumes a lot of alkalinity. When the dKH drops that low (5.3), stony corals can start having problems. It's also useless, because the alkalinity consumption rate varies with the dKH level, so you don't even get good data.

I would dose the dKH up to 7 dKH or so with some baking soda right away. Later today, I'd measure again and bring it up to 8 dKH. This calculator will help with a dose:

I'd then start measuring alkalinity and dosing the two-part by hand at the same time each day, or maybe twice a day if the consumption is high. After a few days or so, you should have a good trend line for alkalinity.

Calcium is harder to manage because there's so much more of it in the water, in terms of making calcium carbonate. 2.8 dKH is consumed for every 20 ppm of calcium. I'd probably test the pumps to make sure that they are dosing the same amount, and let them run with your computed dose for a while, perhaps checking calcium and alkalinity every day for a few days, to make sure the pumps are okay. After a while, you should get a good trend line for calcium, although it might take a few weeks.

Calcium kits often are good only ±20ppm or so, so some patience is required.

Jonathan Bertoni

Last edited by bertoni; 03/31/2013 at 05:22 PM.
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