Very low alkalinity

[Dvir]

Hi,

Running a FOWLR tank for about 8 months now. Tested alkalinity today and it's 4.2 (?!)
These are the changes in measurements from a month ago:

Alkalinity: 6.1 -> 4.2
Calcium: 405 -> 405
Magnesium: 1260 -> 1200
PH: constant at 8.1

Fish look happy as before, should I care?
What can be taking alkalinity so much in a FOWLR tank?

Thanks

 

[Hats_]

whats in the tank and how big is it. tbh i doubt the pH test with alk that low.

 

[Dvir]

whats in the tank and how big is it. tbh i doubt the pH test with alk that low.

9 fishes, angels/tangs/triggers.
Total volume is around 330 gallon.
Using red sea blue salt.
Using Apex PH probe.

Does it even make sense for alk to be that low?

 

[Hats_]

9 fishes, angels/tangs/triggers.
Total volume is around 330 gallon.
Using red sea blue salt.

Does it even make sense for alk to be that low?

i mean, definitely possible. have you tried testing multiple times? what tests do you use for alk and pH?

 

[WrasseyReefer]

How often are you doing water changes? I also use Red Sea blue bucket and the salt alk is 7-8, so if you’re doing water changes, it doesn’t seem likely your alk is actually that low. What’s your salinity?

 

[Oldreefer44]

IMO, always a good idea to verify odd test results by using two different brands of test kits either by way of a local LFS ICP testing or using a different brand yourself. In a FOWLR there is no logical reason for it to change that much without some type of operator error which does not seem likely in this case.

 

[Dvir]

I'll verify with another test kit.
I'm doing about 7% wc every 2 weeks.
Salinity is 1.0245, testing using tropic marin

Alk by Hanna.
PH by apex

 

[Randy Holmes-Farley]

It's very easy to boost alk with sodium bicarbonate (baking soda) or sodium carbonate. I cannot see any reason to not do that.

 

[Dvir]

It's very easy to boost alk with sodium bicarbonate (baking soda) or sodium carbonate. I cannot see any reason to not do that.

The baking soda I have at home for food purposes lists sodium hydrogen carbonate e500ii. Not sure what the e500ii is, is it safe to use?

Thanks