Reef Crystal Alk much higher than I thought.

Joe31415 · Oct 10, 2021

I've been using Reef Crystals since day 1, which would have been about the end of last year. For as long as I've been tracking Alk (Dec 29th, 2020), it's always been in the 8-9 range. These days, there's 7 or 8 growing corals, and the alk still typically stays at 8-9. Occasionally dipping into the high sevens, in which case I'll add a bit of alk to it. The only water changes I'm doing these days is maybe a gallon or two a week, usually just trying to correct the water height because I was adjusting something else.
In any case, on a whim, I tested the alk of my invert QT. Right now, it's full of snails (and a tiny blue leg hermit crab that hitchhiked in on a snail) and 3 frags. The alk in the tank was 11. I thought maybe I made a mistake and did a second test. 11 again. Looking back right now, the alk on the invert QT has always been higher, usually in the high 9's. I do much more substantial water changes in that tank on a much more regular basis.

I checked the alk of the mixing tank. It was 12 and 'the internet' seems to confirm that Instant Ocean Reef Crystals do measure around 11-12.

So, here's my question. Is my DT going through enough alk that it originally ran it down from 12 to 8 that's where I happened to be maintaining it? Should be dosing it up higher to be closer to the reef crystals? Should I switch to a different salt?
What about the QT, stick with Reef Crystals and stick with my DT's alk numbers, should I lower the QT alk and if so, how?

And while we're here. A side question. When you use 2-part, do you always dose both alk and calcium? I've only added alk one or two dozen times, but I've only added calc two or three times. (maybe I need to measure the calcium in my mixing tank. I'll bet it's really high)

mdb_talon · Oct 10, 2021

If your DT is good and has healthy growing corals i see no reason to think of changing. Assuming you are not doing really large percentage water changes using a high alk salt into your moderate alk display is not going to cause a huge jump....and probably is keeping it stable in that 8-9 range. If you switch to a low alk salt then you would need to dose more(or settle into a lower alk in display).

In theory alk/calc should be dosed in equal amounts. Since there is a lot more calc in the water it sometimes appears it drops slower. In some cases tanks do actually use more alk from some biological processes but over long term they should be pretty close as i understand it(and in my experience)

Joe31415 · Oct 11, 2021

mdb_talon said:
If your DT is good and has healthy growing corals i see no reason to think of changing. Assuming you are not doing really large percentage water changes using a high alk salt into your moderate alk display is not going to cause a huge jump....and probably is keeping it stable in that 8-9 range. If you switch to a low alk salt then you would need to dose more(or settle into a lower alk in display).

No big changes. At the beginning I was doing a gallon or two a day, but someone mentioned that for a new tank, I'm not giving the nutrients a chance to build up a little.
I think my concern (and panic) was at finding out how big of a difference there is between my DT and QT. So far I've never lost anything moving into the QT and in fact most things start doing much better, but I always attributed that to a bigger, more established tank (which it probably is).

As for adding calcium and alkalinity. The few times I've added calcium, based on my notes, I was adding about 100ml of calcium to 10ml of soda ash (based on the BRS calculator).