Alk Testing

Bozburn · May 22, 2023

Wanted to get the forum's input.

A few weeks ago I set up my Trident since I have now put SPS in my tank and I need to dial it in to keep these things alive (so far I've had a few that are doing well and a good handful that are not doing well).

I set up the trident, calibrated it and got it running and I do manual testing every weekend to double check so I did that.

As of today my Alk is all over the place with 3 different test kits. Trident says 7.16, Salifert says 7.7 and Hannah says 8.29. Which do I go off of? I did 3 tests of the trident and Hannah the other day and they averaged about the same and I got the Salifert today, but I want to make sure I get it right since I'm trying to dose and keep it around 8.

Also, I don't trust Hannah that much. The salinity thing I got was way off and I calibrated it once a week.

For the SPS my calcium is around 450 and Mag is around 1350, trying to bring that up a bit.

Thanks!

fishski13 · May 22, 2023

To be honest, its odd that you are getting three different results that are that far apart, however it best you just use one test kit that is going to give you consistent results. Say if you use the trident and you trust it the most, than dose or keep levels at 8 just dependent on that source. This will ensure levels are consistent, which consistency is more important than chasing that magical number.

Randy Holmes-Farley · May 23, 2023

FWIW, folks have trouble with Trident values sometimes, especially if reagent gets low.

Fortunately, all of those values are fine.

TurboTang · May 23, 2023

My trident consistently reads 0.5 lower than Hannah. I've personally seen little/no change with new reagents. I started at 8.0 Hannah / 7.5 trident. Slowly I've balanced it to 8.3 / 7.8. maybe one day I will spring for an icp and get a third "opinion"

Bozburn · May 23, 2023

I've got an ICP so I might go ahead and do that. I want to start the reef moonshiners program here soon as well, so that might help figure out which one is correct.

I am leaning towards salifert since its chemicals and has no mechanical hardware that could be calibrated wrong. Thanks everyone!

JimWelsh · May 23, 2023

TurboTang said:
My trident consistently reads 0.5 lower than Hannah. I've personally seen little/no change with new reagents. I started at 8.0 Hannah / 7.5 trident. Slowly I've balanced it to 8.3 / 7.8. maybe one day I will spring for an icp and get a third "opinion"

Hannah reading 0.5-1.0 higher than a well-calibrated Trident is a widely reported phenomenon. Also, ICP can't measure alkalinity. They're just doing another titration.

Bozburn said:
I've got an ICP so I might go ahead and do that. I want to start the reef moonshiners program here soon as well, so that might help figure out which one is correct.

I am leaning towards salifert since its chemicals and has no mechanical hardware that could be calibrated wrong. Thanks everyone!

How do you know you're choosing the correct endpoint color? That can make a big difference. Most people overshoot the Salifert test, giving a slightly high reading.

Bozburn · May 23, 2023

JimWelsh said:
Hannah reading 0.5-1.0 higher than a well-calibrated Trident is a widely reported phenomenon. Also, ICP can't measure alkalinity. They're just doing another titration.

How do you know you're choosing the correct endpoint color? That can make a big difference. Most people overshoot the Salifert test, giving a slightly high reading.

Good point, I will likely do 3 salifert tests back to back to back to verify. It was fairly obvious when the color changed.

The salifert and Trident were somewhat close to each other so I will likely rely on those two moving forward to try and keep consistency.

JimWelsh · May 23, 2023

Bozburn said:
It was fairly obvious when the color changed.

Alkalinity titration endpoint pH & Salifert endpoint color

TL;DR: The endpoint pH is 4.41, and the endpoint color is that "lavender" color I've been telling people about. Over the years, there have been many threads on R2R and other forums debating a couple of basic details relevant to testing for alkalinity in reef aquaria. One of the most...

www.reef2reef.com

TurboTang · May 23, 2023

JimWelsh said:
Hannah reading 0.5-1.0 higher than a well-calibrated Trident is a widely reported phenomenon. Also, ICP can't measure alkalinity. They're just doing another titration.

How do you know you're choosing the correct endpoint color? That can make a big difference. Most people overshoot the Salifert test, giving a slightly high reading.

Yeah I realize that about the icp and that's why I called it another "opinion". But I think it's a better path for me than buying another brand alk test.

Randy Holmes-Farley · May 23, 2023

TurboTang said:
Yeah I realize that about the icp and that's why I called it another "opinion". But I think it's a better path for me than buying another brand alk test.

IMO, this is the best bet, if you have a pH meter. You can use a large tank water volume and a standard acid to minimize errors.

A DIY Alkalinity Test: By Randy Holmes-Farley - REEFEDITION

Alkalinity is one of the most important measurements that a reef aquarist can make. It can become rapidly depleted in many aquaria, requiring frequent measurement in order to maintain stable levels.

www.reefedition.com