alk swings

rayn · Sep 30, 2014

Saturday night I did a water change on my 20 gallon. Sunday I tested everything. Traces were 0. Cal was 380. Mag was 1290. Alk was 9.8 dkh. All done with red sea test kits. Phosphate was .03 with Hanna checked. Tonight I test alk, my biggest concern it seems lately, and it is down to 5 dkh! Two days dropped almost 5 dkh?! Now I don't have much, anemone, couple soft corals, couple acans, nothing major. Cal and mag seem to be able to hold steady.

What gives? Do I really need to dose nightly?

jolt · Sep 30, 2014

When I get that big of a swing I definitely re-test. I've made mistakes before and simply gotten a bad reading ...

rayn · Sep 30, 2014

jolt said:
When I get that big of a swing I definitely re-test. I've made mistakes before and simply gotten a bad reading ...

Same here. That is after two tests, both the same result.

Randy Holmes-Farley · Oct 1, 2014

Many tanks can drop 2.5 dKH per day, even with just strong growth of coralline algae and some soft corals, but it seems fairly unlikely given your description. How long has the tank been set up?

However, alk doesn't usually drop much below 6 dKH even with no dosing because calcification slows way down.

Are you dosing anything? Many people do dose every day, or even multiple times per day.

In terms of repeat testing, you can repeat the 5 dKH, and assuming the procedures were correct and the kit isn't faulty somehow, you still cannot repeat the earlier reading. Maybe it was the one that was off.

What salt mix are you using? My first qaction would be to try the kit on the new salt mix to make sure it is giving reliable results.

enrique · Oct 1, 2014

Randy, can I put some bicarbonate sodium (1 dkh value for my tank) in the RO/DI I use to mix salt every time I make new saltwater so everytime I make a water change (10% once a week) I can kepp my Alk up?

rayn · Oct 1, 2014

Randy, the first reading was after a low reading as well. I dosed and got it up to 9ish. Then two days go by and I was down to 5. I dosed slowly overnight and tested this morning and was back up to 9. Dosing was with baking soda. Tonight I check after being gone for 12 hours and it was back down to 7.5. Dosed the recommended dose of 1/2 tsp baking soda, and it is back to 9.

I am assuming then I need to dose 1/2 tsp daily to keep the level of 9 dkh.

Randy Holmes-Farley · Oct 2, 2014

enrique said:
Randy, can I put some bicarbonate sodium (1 dkh value for my tank) in the RO/DI I use to mix salt every time I make new saltwater so everytime I make a water change (10% once a week) I can kepp my Alk up?

Your salt mix probably already has quite a bit of alkalinity in it (often much more than NSW), and I'd be reluctant to add more to it due to potential precipitation of calcium carbonate.

I'd just add it to the tank, dissolved in some RO/DI.

Randy Holmes-Farley · Oct 2, 2014

rayn said:
Randy, the first reading was after a low reading as well. I dosed and got it up to 9ish. Then two days go by and I was down to 5. I dosed slowly overnight and tested this morning and was back up to 9. Dosing was with baking soda. Tonight I check after being gone for 12 hours and it was back down to 7.5. Dosed the recommended dose of 1/2 tsp baking soda, and it is back to 9.

I am assuming then I need to dose 1/2 tsp daily to keep the level of 9 dkh.

That sounds like a reasonable conclusion.

What size tank?

enrique · Oct 2, 2014

Randy Holmes-Farley said:
Your salt mix probably already has quite a bit of alkalinity in it (often much more than NSW), and I'd be reluctant to add more to it due to potential precipitation of calcium carbonate.

I'd just add it to the tank, dissolved in some RO/DI.

Thanks!