Why is my Alk dropping but not my Ph?

[Randy Holmes-Farley Verified Community Expert]

He also suggested that my corals would have used the Alk which I'm ok with, but until now I thought by doing that, it would lower Ph at the same time? That's also how I was checking my levels everyday, by looking at the Ph on the monitor.

Judging alkalinity by pH is not a good plan. They do not need to move together.

 

[Randy Holmes-Farley Verified Community Expert]

I would like to raise my Alk a bit, at least to 8 to be like before, but it's also gonna raise the Ph (which is still sitting at 8.13).

I would not worry about the pH rise. You are actually low in pH and would benefit from a rise. Unless your pH is above 8.5, there's no reason to be overly concerned about pH.

 

[taricha]

Ph is at 7.8 at night, and rises to 8.13 during the day.
Today I decided to measure my Alk with my Hanna checker, and discovered that it's sitting at 6.3, which is very different than the 8.2 I'm used to.

These numbers are unlikely to both be correct. (8.13pH and 6.3 dKH)
you can play around with this simulation
Ocean Alk, pH, Carbon
at Alk of 6.3 (2250 microequivalents/L on the sim) your CO2 would have to be impossibly low (well below outdoor air 400ppm) to get a pH of 8.13.

I'm saying figure out which of Alk or pH is leading you astray before you start changing a bunch of things.

edit: didn't see randy's advice above, to fix your alk and let pH handle itself. Probably a better more practical plan than spending a lot of time chasing test errors.

 

[Broutilde]

These numbers are unlikely to both be correct. (8.13pH and 6.3 dKH)
you can play around with this simulation
Ocean Alk, pH, Carbon
at Alk of 6.3 (2250 microequivalents/L on the sim) your CO2 would have to be impossibly low (well below outdoor air 400ppm) to get a pH of 8.13.

I'm saying figure out which of Alk or pH is leading you astray before you start changing a bunch of things.

edit: didn't see randy's advice above, to fix your alk and let pH handle itself. Probably a better more practical plan than spending a lot of time chasing test errors.

I feel like before implementing any radical changes, I should check if my alk checker is working properly like you suggested. I've been raising my alk a little bit so it reaches 7 already, and today I'll bring my water to a friend, see what he finds out.

 

[Broutilde]

Well, Hanna checker wasn't faulty, so I started raising my Alk slowly. I'll see how it goes, but I still find it very unlikely that Alk dropped from 8 to 6.3 in one week, as I only have small frags in a 25 gallons.

 

[HuduVudu]

Well, Hanna checker wasn't faulty, so I started raising my Alk slowly. I'll see how it goes, but I still find it very unlikely that Alk dropped from 8 to 6.3 in one week, as I only have small frags in a 25 gallons.

You would be surprised. In my experience once the coral adjusts to conditions they seem to want to make up for lost time and will start pulling what they need. Then it seems once the backlog is over the back down. This has caused a ton of rubber banding with me. Took me a while to figure it out. Now I watch for it and ramp up slowly.

 

[clffthmps]

Keep in mind, don’t chase numbers.what works for one tank might not work for another.All tanks run different.If coral and fish are happy and doing well.Take your time.

 

[Broutilde]

Keep in mind, don’t chase numbers.what works for one tank might not work for another.All tanks run different.If coral and fish are happy and doing well.Take your time.

I agree with that, and I just want my numbers to be like before, I'm really aiming at stability. It was working well for my corals at that Ph (8.13) and that Alk (8.5), but I guess I have to find a new normal now! Just like with Covid19

 

[92Miata]

Well, Hanna checker wasn't faulty, so I started raising my Alk slowly. I'll see how it goes, but I still find it very unlikely that Alk dropped from 8 to 6.3 in one week, as I only have small frags in a 25 gallons.

How old is the tank?

There are a bunch of things (like the nitrogen cycle) that are alkalinity neutral in a mature tank, but consume alkalinity in new tanks.

I'd just up my dosing a couple ml and test daily for a bit and let it creep back up.

 

[Broutilde]

How old is the tank?

There are a bunch of things (like the nitrogen cycle) that are alkalinity neutral in a mature tank, but consume alkalinity in new tanks.

I'd just up my dosing a couple ml and test daily for a bit and let it creep back up.

It's five months so fairly new indeed