Help - Alkalinity Rising Mystery

[Jeremy Luke]

My alkalinity has been gradually raising over the paste few months. Previously I was dosing alk and calc daily and uptake was fine. I had an ich problem and moved all fish to a quarantine tank. The problem started during the fallow period. I struggled keeping nutrients in the water column. I lost a couple of frags. Then the rising alkalinity. I stopped dosing almost 2 months ago. I later unplugged my dosers just to make certain they weren't somehow dosing. The fish went back in a few weeks ago. Already the corals are gaining color back and looking better but the alkalinity keeps creeping upward. I just went four weeks without changing water. The alkalinity over that time went from 9 to now 10 dkh. I just went with a new salt for my 20% water change last night. I used blue bucket red sea for it's low alk. I'm going to change another 20% tomorrow night. I'm going to continue to do water changes until I can get it back down under 9 and I guess I'll manage it this way.. but seriously, what's going on?

Temp: 78
sg: 1.025
Alk: 10dkh
Calcium: 420
Magnesium: 1400
Phos: .06
Nitrate: 5ppm

 

[Randy Holmes-Farley Verified Community Expert]

Alkalinity must come from somewhere. It cannot just "rise".

You are dosing nothing?
Are you measuring the alk in the new salt water?
Do you use tap water for top off or for the new salt water? Tap water often has alkalinity in it.
Has nitrate declined a lot during this time (denitrification adds alkalinity).

 

[Jeremy Luke]

Alkalinity must come from somewhere. It cannot just "rise".

You are dosing nothing?
Are you measuring the alk in the new salt water?
Do you use tap water for top off or for the new salt water? Tap water often has alkalinity in it.
Has nitrate declined a lot during this time (denitrification adds alkalinity).

Hi Randy. Yes, I'm not dosing anything now. I have about 20 frags in the tank most around 1.5" a few around 3".
The IO batch I was using measured 11dkh. I did not do a water change for 4 weeks and the alkalinity still rose during that time. I used blue bucket red sea last night to do a 20% change. I did not measure it first. I'm going to make another big batch tonight and will measure tomorrow before I use it.
I am using a BRS 5 stage RODI unit to make the water for my water changes.
The nitrate did decline during this time due to the fallow tank. Over the past couple of weeks it has been rising due to the fish going back in the tank but perhaps the alkalinity issue was due to the nitrate drop although it only went from 10ppm to undetectable during that fallow period.

 

[five.five-six]

What's the expiration date on your test kit? You might want to take a water sample to your LFS for verification.

 

[Jeremy Luke]

What's the expiration date on your test kit? You might want to take a water sample to your LFS for verification.

I am using two test kits. Elos and Red Sea Pro to verify. I just received a new Red Sea Pro refill kit recently from BRS. Both tests give me the same results.

 

[eshtog]

Literally the same exact scenario is playing out in my tank. Tank is fallow and I’m not dosing anything. Alkalinity kept creeping up all the way until 10.92 I then decided to do a 40% water change which brought down the alk to 9.26 Now 6 days later and Alk is back up to 9.64 What could be causing this? Did anyone with this problem figure it out?

 

[SeaDweller]

Are you feeding the tank although it’s fallow? Corals might not be up-taking alk and ca for growth if there’s no N and P in the water, which is needed. If your tank has no NO3 and PO4, then you may need to dose or ghost feed the tank.

 

[Bonsai reef]

Are you buying water from LFS? My LFS once messed up giving me buffered water instead of plain RO and the buffered water had 15+ dKh of alk!

 

[Bonsai reef]

Are you buying water from LFS? My LFS once messed up giving me buffered water instead of plain RO and the buffered water had 15+ dKh of alk!

never mind. i just noticed you are making your own water.

 

[Braves Fan]

Double check your salinity meter had this happen to me ,, my salinity meter was off and I was using a higher Alk salt ,, doing 2 water changes a month ,, the Alk number just kept going up ,, I felt so stupid for not figuring this out