Alakalinity Spikes

jordanrb · 2026-09-15T11:20:30-0400

I dose AFR in my tank daily and have been doing so for a while now. Alkalinity stays pretty stable with a .1 drop every 2 days. I have not changed my AFR dosing as by the time I do a water change it goes back to the original number. So I am looking at a change of .4-.5 every 1.5 weeks which is very good.

However the last month I have experienced a random jump in Alakalinity overnight twice. Usually around the 1.5 week mark after my WC. I have no idea what is going on. My alkalinity is doing the slow consistent drop than all of a sudden it spikes back up.

The only thing I am dosing is 5ml of magnesium and calcium weekly. However I did dose both yesterday and by this morning my alkalinity spiked 0.4 from 8.2-8.6. From my understanding the magnesium and calcium should not cause the spike.

The only thing I can think of is my AFR dosing is too high and it just takes a while to kick in but from what I read that is not how it works. If I lower my dose the dialy alkalinity drop will just be higher.

Randy Holmes-Farley · 2026-09-15T11:29:52-0400

Can you clarify what exact brands of what you dosed in the several days before this alk result?

It is most likely a testing issue, but let's be sure.

jordanrb · 2026-09-15T11:40:34-0400

Randy Holmes-Farley said:
Can you clarify what exact brands of what you dosed in the several days before this alk result?

It is most likely a testing issue, but let's be sure.

I dose 5ml of aqua vitro magnesium and calcium yesterday evening and this morning after testing alkalkinity it showed the spike.

I have a 20g tank so it is a very small dose of both.

I use Hanna checkers for everything and am fairly consistent. When I see an alkalinity spike I double check and it reads the same every time within .1 of each test.

Randy Holmes-Farley · 2026-09-15T12:24:43-0400

jordanrb said:
I dose 5ml of aqua vitro magnesium and calcium yesterday evening and this morning after testing alkalkinity it showed the spike.

I have a 20g tank so it is a very small dose of both.

I use Hanna checkers for everything and am fairly consistent. When I see an alkalinity spike I double check and it reads the same every time within .1 of each test.

If you dosed this product, it will boost alkalinity to some degree, and I advise against using it. It is a remarkably poorly designed and described product.

https://www.aquavitro.com/calcification.php

jordanrb · 2026-09-15T12:41:43-0400

Randy Holmes-Farley said:
If you dosed this product, it will boost alkalinity to some degree, and I advise against using it. It is a remarkably poorly designed and described product.

https://www.aquavitro.com/calcification.php

That is the product I use. I really appreciate that. I had no idea. I was told it is pure calcium

Randy Holmes-Farley · 2026-09-15T12:49:36-0400

jordanrb said:
That is the product I use. I really appreciate that. I had no idea. I was told it is pure calcium

Don't know who told you that, but Seachem does not understand their own product.

It contains (by their info):

A concentrated (140,000 mg/L) optimized blend of ionic and bioavailable gluconate-complexed calcium

What do they think happens to the gluconate? It is metabolized by bacteria to produce alkalinity. I told this to them many years ago, but they did not change their product or its description.