what test to trust

[bobt2]

I bought a hanna handheld for alk. it says the alk is 7.2 dk. the salifert says 9.1. I have gone by the salifert for years and have a great reef with lots of coral growth. how do I know what to believe?

[mcgyvr]

Assuming that both reagents are not expired and that you have performed more than one test and that you are testing correctly you trust neither at this point.. Get another test done to compare.. Got a fish store close that can test alk for you?
Bring your test kits to run all 3 at one time..

[Uncle99]

Originally Posted by bobt2

I bought a hanna handheld for alk. it says the alk is 7.2 dk. the salifert says 9.1. I have gone by the salifert for years and have a great reef with lots of coral growth. how do I know what to believe?

I doubt the 7.2 number, you would not have had great success with that number

[mcgyvr]

It wouldn't be a bad idea to also post a picture of exactly how much liquid you put into the syringe during testing.. You may be reading/filling incorrectly..

[heritage]

http://www.reefkeeping.com/issues/2004-05/rhf/index.php

[bobt2]

the hanna is a led meter. it measures the color of the sample. there are no chemicals, and no way to calibrate

[bobt2]

btw, it is brand new 2 weeks, and the same thing has happened since the beginning

[heritage]

How old is the salifert ?
I would check your results against a third kit.

[bobt2]

salifert is in date.but yes. I need a 3rd test to know.

[NanoGeek0815]

You could always pick up a calibrated solution and find out which one is closer.

Sent from my SM-G975U using Tapatalk

[JWClark]

You use the same vial and sample for both the calibrate/control sample and the test sample w/ reagent? If not, I would not trust, if so, I would.

They give you two vials and a common mistake is using one for the first read and then the second w/ reagent for the second read. The test is all about measuring the refraction of light in the sample before the reagent is added--the control--to that after the reagent is added.

Using different vials/samples for these two steps introduces variability into the equation from vial imperfections and differences in the samples themselves. Best technique is to wear gloves, rinse the vial w/ tank water first, then add the tank sample (and measure w/ a pipette or something similar--NOT the line on the vial). Wipe the vial w/ a lint free cloth and ensure no air bubbles. Place vial in reader when instructed w/ the "10ml" facing forward. When instructed, remove vial, add the reagent, and gently invert 5-6 times to mix. Then wipe w/ lint free cloth again, check for air bubbles, and put back into reader w/ the "10ml" facing forward (this allows you to standardize the glass thickness).

Following this method I would trust over Salifert. I have always had trouble detecting the color change on their alk test which is why I switched. Other tests are fine (Ca and Mg).

Also, my tank runs about 7.6 and it is doing great. You could have had great success w/ an alk of 7.2 if it was stable. If I remember right, my alk was lower than what the Salifert was telling me too but I'd have to dig back through my logs to verify.

[bobt2]

thanks, yes I do use the same one for both.i will try again, checking what you said

[five.five-six]

There has to be something quite wrong with either your methodology or the reagents in either one or both tests. .5 DKH variation would be unsurprising, anything over .75 would give me pause for concern. They are both very high quality kits and I would expect them to be very close if not exact. As mcgyvr said, I wouldn’t trust either until you get this figured out.

[five.five-six]

Originally Posted by JWClark

Also, my tank runs about 7.6 and it is doing great.

This^

I shoot for 8.0 DKH. Really the only reason to run at 9-10 is if you are having pH problems or going for slightly extra fast growth rate but running 9+ leaves you exposed to al sorts of potential problems that could be dogistrophic. Dip in nutrient levels, dip in Mg levels or a spike in alk can be much more harmful much faster if you are starting from a point of 10.0 DKH than if your starting point was 7.5-8.0.

[bobt2]

I ordered the color standard from hanna.at this point, since the tank has been fine for years I will believe the salifert. I,m sorry I tried upgrading to newer tech testing.

[JWClark]

Originally Posted by five.five-six

There has to be something quite wrong with either your methodology or the reagents in either one or both tests. .5 DKH variation would be unsurprising, anything over .75 would give me pause for concern. They are both very high quality kits and I would expect them to be very close if not exact. As mcgyvr said, I wouldn’t trust either until you get this figured out.

Agree. Another thing with Salifert I noticed was sometimes my readings got a little off when I was near the bottom of the titrating reagent bottle. Always assumed evaporative loss over the 6 months or so for me to use it up just concentrated the solution--changing results over time.

But would assume this would cause a lower than actual reading since you would get color change sooner.

0.762 out!

[boxfishpooalot]

Hey make your own check solution its in my signature.

[hkgar]

Originally Posted by bobt2

the hanna is a led meter. it measures the color of the sample. there are no chemicals, and no way to calibrate

There is a calabration checker for the Hanna.
https://www.saltwateraquarium.com/hi...YaAgOvEALw_wcB

[bobt2]

ordered, thanks

[hkgar]

You're welcome

[bobt2]

update. I got the calibration standard from hanna. according to tha,t the hanna meter is within spec, so the salifert was reading high and I will trust the hanna.

[Uncle99]

You have a 2 DKH difference, since everything looks good I would make that change real slow.

[hkgar]

Generaly not more than .5 dKH/day.

[bobt2]

yea, but I only want 8 so less than 1 dk. i think part of the issue is the corals are really getting bigger, so they are using more than before and i have to increase the daily dose