High alk and low mag

[bgilson]

Last week I tested my water and had similar issues. So monday I did a 50% wc on my 75gal. Tested the water today and these were my results. My phosphates have been high for a little while. I believe due to a missing fish but I use rowaphos to keep it down. I cant figure out why alk is high and mag is low. I use tap water and prime for wc. Any suggestions would be appreciated.

 

[TX_REEF]

What’s your method of testing? I’d also be concerned about your salinity

 

[bgilson]

What’s your method of testing? I’d also be concerned about your salinity

Hanna for all. Salifert alk as 2nd opinion. I typically run 1.025 but I didnt get it spot on mondays wc

 

[TX_REEF]

There’s no reason for kh to be that high realistically. What salt do you use?

 

[Randy Holmes-Farley Verified Community Expert]

I don' t believe the magnesium is accurate and it's time to start RMM:

https://www.reef2reef.com/threads/just-say-no-to-magnesium-testing-rmm-is-born.1017528/

 

[Randy Holmes-Farley Verified Community Expert]

Tap water can contain considerable alkalinity and may be why it is high.

Try measuring the alk of your tap water. You may need to switch to a purified water.

 

[bgilson]

Tap water can contain considerable alkalinity and may be why it is high.

Try measuring the alk of your tap water. You may need to switch to a purified water.

The tap water alk showed 10.9 yesterday when I tested it

 

[bgilson]

There’s no reason for kh to be that high realistically. What salt do you use?

Instant ocean reef crystals. I have always used that salt.

 

[Randy Holmes-Farley Verified Community Expert]

The tap water alk showed 10.9 yesterday when I tested it

Serious problem. Take 11 dKH salt mix and 10.9 dKH tap water and get 22 dKH new salt water.

If you really want or need to use tap water, at least knock out the alk in it with acid, aerate it to drive out the newly excess CO2, and then use it.