Alk drop after water change

[svreef]

I did a 20g water change yesterday (175g system volume) and alk dropped from 7.2 to 6.8 according to the Trident. I have All For Reef. Should I dose?

I tried dosing it last week - started at 7.2 and a single dose of 30ml raised it to 7.4. It was back to 7.2 in 7 days.

 

[ofzakaria]

I did a 20g water change yesterday (175g system volume) and alk dropped from 7.2 to 6.8 according to the Trident. I have All For Reef. Should I dose?

I tried dosing it last week - started at 7.2 and a single dose of 30ml raised it to 7.4. It was back to 7.2 in 7 days.

That might indicate a low salinity on the new batch. Or low dkh on the new salt mix.

 

[svreef]

Salinity was higher in the new batch. Tank was 1.024, new batch 1.026 intentionally because I want to get to 1.025. Didn’t test alk on new batch.

 

[ofzakaria]

Just to be sure, i would double check your salinity measurment method

 

[thanh510]

Are you using any other test methods? I know for trident, that's within it's margin of error. Have subsequent test's been the same? When this happens, I bust out my Hanna. Also low regents will throw off the readings by at least 1dkh.

 

[svreef]

Reagents are high and there was a test at midnight and another at 6am. I could double check, but nothing else has changed.

Trident claims +-0.05 dKh

 

[thanh510]

Reagents are high and there was a test at midnight and another at 6am. I could double check, but nothing else has changed.

Trident claims +-0.05 dKh

I think their margin of error if you do maximum amount of testing. I have not seen that maybe it's my unit?

 

[IOnceWasLegend]

Salinity was higher in the new batch. Tank was 1.024, new batch 1.026 intentionally because I want to get to 1.025. Didn’t test alk on new batch.

How long did you leave your new batch mixing?

I was curious recently and mixed up a batch. dKH after 24 hours was 12. After 48 hours, 10.4. After 72 hours, it was 9.8. Salinity was held constant at 1.026 for each measurement.

 

[svreef]

1.024 with Milwaukee and refractometer

 

[Coral reefer]

How long did you leave your new batch mixing?

I was curious recently and mixed up a batch. dKH after 24 hours was 12. After 48 hours, 10.4. After 72 hours, it was 9.8. Salinity was held constant at 1.026 for each measurement.

Which salt was this?

 

[IOnceWasLegend]

Which salt was this?

IO regular. Though I was under the impression this was common in all salts with continued mixing.

 

[svreef]

Mine was in a brute, covered with a power head for over a week before I used it.

 

[ofzakaria]

Needless to say you need to cross correlate the kh reading with another trusted kit. Just to be safe. I thought you already cross checked your kh reading.
Before you tinker with anything you need to make sure the reading is correct.
Run a kh reading with the trident then at the same time do a kh test using trusted kit then compare the values.
Kh vary during the day so when you cross correlate you need both measurments within similar time

 

[svreef]

Hannah says 7.3 dKh. Ugh. Will try salifert and then calibrate the Trident

 

[thanh510]

Hannah says 7.3 dKh. Ugh. Will try salifert and then calibrate the Trident

Mines is off about .3 give or take from Hannah. When it veered to over 1, that’s when I recalibrated. So as long as trident stays near and consistent with every subsequent test.

There was another thread that mentions the needle being slanted. I would check that too.


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[ofzakaria]

Hannah says 7.3 dKh. Ugh. Will try salifert and then calibrate the Trident

Make sure you compare measurments similar in time.

 

[Newjack]

its pretty common to happen during water changes unless you buffer the new water to the exact DKH that matches your tank perimeters. Its no biggie.. If the tank drops in DKH after a water change, just add an Alk solution of your choice to bring it back to where you want it.

 

[ofzakaria]

its pretty common to happen during water changes unless you buffer the new water to the exact DKH that matches your tank perimeters. Its no biggie.. If the tank drops in DKH after a water change, just add an Alk solution of your choice to bring it back to where you want it.

I would not add alk before I confrim measurment is correct.
It's not very common to have alk swing after water change unless if the new mix have less alk..much less i must add since water change is at most 20%.
Since op said he mixed his salt at even higher salinity it make no sense to see a drop in the alk i would expect higher alk and ca since the salt mix is at higher salinity.
Confirm measurement then take action..

 

[svreef]

Calibrated the Trident and it got accurate readings per the solution.

After the calibration:

Trident says 6.7 dKH
Hannah says 7.3
Salifert says 7.1

If I can’t trust the Trident to measure accurately, it’s a huge waste of a lot of $

Where do I go from here?
Dose Alk until Trident reads above 7?
Then, I know for sure it’s above 7 no matter what. And I can use Trident’s measurements to hold it steady.

 

[thanh510]

Trident is always going to be off from Hannah and Red Sea. Too many variables with all three test. But Hannah has been very consistent.

I don’t think it’s a waste of money. It’s consistent 80% of the time. You can tell when it’s off! It helps that it does 4 or more test a day. When it varies drastically, I bust out the Hannah. I test Hannah once or twice a month. Far less than without the trident. That’s what the automatic testers will do for you, gives you back some time from testing.

You should start dosing alk. With trident paired with dose, it tries to keep it within a certain parameter. But only within 10% of what you set the dosing to be.


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