Alk keeps dropping

[Grootzilla]

Hey all! I currently am facing issues with low parameters and don’t really understand why.

My tank is a 14 gallon with some gsp, a single rock flower anemone, a single bubble tip anemone, two clowns, a tuxedo urchin and a tiger pistol shrimp. It is lit with an AI Prime 16 and I also have an mp10 to provide flow. My nitrates are sitting at a solid 10ppm and phosphates are also low(undetectable with saliftert test kit).

My issue is that last week I checked my alkalinity because my BTA was looking a little ticked off and it was at 6.9dKH. I also checked calcium and mag and those were also very low. I use the reef pro Red Sea salt and have been doing a bunch of water changes recently so I was totally caught off guard. I immediately did a water change and retested my alk and it was up to 7.5dKH. I decided to leave it there because my work week was starting and I would have more time in a few days to do another water change and bring it up higher. I tested my alk just now and it was at 6.3dKH. I did the last water change on Friday. Nothing in my tank would be using calcium and alk to build a skeleton so I am stumped. Is my salt precipitating out in the water column?

 

[Randy Holmes-Farley Verified Community Expert]

There are users you do not see, and an urchin will likely use alk (no one ever talks about it, but its shell (its test) and its spines and teeth are calcium carbonate).

Also, the accumulation of dissolved organics will lower alk, as will rising nitrate that is kept in check by water change.

I'd just add a little baking soda periodically. This calculator shows how much:

Reef Chemistry Calculator

 

[Grootzilla]

There are users you do not see, and an urchin will likely use alk (no one ever talks about it, but its shell (its test) and its spines and teeth are calcium carbonate).

Also, the accumulation of dissolved organics will lower alk, as will rising nitrate that is kept in check by water change.

I'd just add a little baking soda periodically. This calculator shows how much:

Reef Chemistry Calculator

I did a water change yesterday and my alk was brought up to 8.5. I tested again today and it’s dropped down to 7.3. My lights only turned on 30 minutes ago. Given how fast these swings are and there really isn’t much in the tank that should be absorbing any alk or calcium I don’t really understand how it’s dropping this dramatically.

 

[AFHokie]

I did a water change yesterday and my alk was brought up to 8.5. I tested again today and it’s dropped down to 7.3. My lights only turned on 30 minutes ago. Given how fast these swings are and there really isn’t much in the tank that should be absorbing any alk or calcium I don’t really understand how it’s dropping this dramatically.

What are you testing with?

That much drop that fast suggests testing error.

 

[Uncle99]

When results are unexpected, always check with another kit.
Sometimes test kits send us running in many directions which usually culminate in water instability.

 

[Grootzilla]

What are you testing with?

That much drop that fast suggests testing error.

A Hanna checker. I just got new reagent, though I think I didn’t screw on the cap right once and so it was open for a few days. That may be the issue :’)