ATI ICP Test and Alkalinity

[JayFish4004]

My alk from the ATI ICP test has been consistently about half a point under my Hanna Checker. Hanna is showing 8.0 and typically the ATI would be 7.5.

The latest test I just got the results from show it a full point under at 6.8 somehow - difference this time being it took a few extra days to get to Germany in the mail.

With a salt that mixes at 8.0 and 15% weekly water changes in a 20 gallon tank - wouldn’t it be nearly impossible to be at 6.8 unless I was dosing something acidic and not countering it?

I also have very little consumption - maybe drops 0.3 in 2 weeks if I dont change the water.

 

[gbroadbridge]

An ICP does not test Alkalinity.

ATI must be testing Alk using another method such as an acid titration.

The Hanna accuracy is +-0.4 dKh, so the difference to ATI is insignificant.

The last test reading was probably a measurement error with the Hanna.

 

[JayFish4004]

An ICP does not test Alkalinity.

ATI must be testing Alk using another method such as an acid titration.

The Hanna accuracy is +-0.4 dKh, so the difference to ATI is insignificant.

The last test reading was probably a measurement error with the Hanna.

Measurement error with ATI you mean?

Over last 3 days with Hanna its been 7.9, 7.9 and today 8.0

 

[mdb_talon]

My alk from the ATI ICP test has been consistently about half a point under my Hanna Checker. Hanna is showing 8.0 and typically the ATI would be 7.5.

The latest test I just got the results from show it a full point under at 6.8 somehow - difference this time being it took a few extra days to get to Germany in the mail.

With a salt that mixes at 8.0 and 15% weekly water changes in a 20 gallon tank - wouldn’t it be nearly impossible to be at 6.8 unless I was dosing something acidic and not countering it?

I also have very little consumption - maybe drops 0.3 in 2 weeks if I dont change the water.

Not impossible at all depending on the timeframe you are talking about.

If in a brand new tank for example you have 8.0 alk and your WC water is always 8.0 then if your dkh drops by .15 every week and you do a weekly 15% water change then the end result is each week your alk will drop by approximately .10 initially and then less as the weeks go on (because the WC becomes increasingly higher alk relative to tank water) until you get to around 7.0 and it would stabilize.

Of course usually the salt mix never is always exactly the same alk and consumption rarely always stays exactly the same, but it shows that over time if you have .3dkh drop biweekly (.15dkh/week) and you do a 15% change weekly then you will end up with an alk around 7 after several weeks. Again this is all else staying the same which it rarely does. 7 vs 6.8 is easily testing MOE (or variation in your salt mix or consumption assumptions).

 

[JayFish4004]

Not impossible at all depending on the timeframe you are talking about.

If in a brand new tank for example you have 8.0 alk and your WC water is always 8.0 then if your dkh drops by .15 every week and you do a weekly 15% water change then the end result is each week your alk will drop by approximately .10 initially and then less as the weeks go on (because the WC becomes increasingly higher alk relative to tank water) until you get to around 7.0 and it would stabilize.

Of course usually the salt mix never is always exactly the same alk and consumption rarely always stays exactly the same, but it shows that over time if you have .3dkh drop biweekly (.15dkh/week) and you do a 15% change weekly then you will end up with an alk around 7 after several weeks. Again this is all else staying the same which it rarely does. 7 vs 6.8 is easily testing MOE (or variation in your salt mix or consumption assumptions).

So is the Hanna Checker wrong telling me 8.0 or us the ATI wrong telling me 6.8? I’ve only heard good things about this Hanna Checker’s accuracy and I would assume at 6.8 my corals wouldn’t be too happy.

 

[mdb_talon]

So is the Hanna Checker wrong telling me 8.0 or us the ATI wrong telling me 6.8? I’ve only heard good things about this Hanna Checker’s accuracy and I would assume at 6.8 my corals wouldn’t be too happy.

Well I dont like the Hanna alk checker at all lol, but I will say the issue with it is usually from reading too low rather than too high from my experiences and those I have read from others. I would be inclined to go with the alk checker numbers for now (though I would definitely get a second test of Salifert, Elos, etc to compare to the Hanna on occasion at least).

In any case with the accuracy of our hobby kits combined with us not usually being able to always do the test exactly the same each time (ie exactly 10.000ml of tank water) which expands that MOE the 6.8 and 8.0 numbers may not be that drastically different.

 

[JayFish4004]

Well I dont like the Hanna alk checker at all lol, but I will say the issue with it is usually from reading too low rather than too high from my experiences and those I have read from others. I would be inclined to go with the alk checker numbers for now (though I would definitely get a second test of Salifert, Elos, etc to compare to the Hanna on occasion at least).

In any case with the accuracy of our hobby kits combined with us not usually being able to always do the test exactly the same each time (ie exactly 10.000ml of tank water) which expands that MOE the 6.8 and 8.0 numbers may not be that drastically different.

Makes sense - Ill bring a sample into my LFS this weekend for a sanity check. My gut is leaning towards the ATI test being off but I also don’t want to assume that without knowing for certain.

 

[gbroadbridge]

Measurement error with ATI you mean?

Over last 3 days with Hanna its been 7.9, 7.9 and today 8.0

No I mean measurement error by both.

Your Hanna reagent batch may be reading low, and that varies by batch and how long the bottle has been open.

My current Hanna batch reads 0.3 dKh high compared to the previous.

Simply because it has a digital display does not mean it is any more accurate than any other hobby grade test kit.

 

[Nburg's Reef]

If it makes you feel better, my Hanna kit is consistently about 0.5 dKH greater than my freshly calibrated Trident and the included trident reagent calibration standard solution.

 

[Borat]

The level does not matter that much - look for stability. My DIY alk tester shows approx. 0.3DKH lower reading than Salifert (unless I stop Salifert titration at lavender colour reading)..

The more worrying thing is if DKH changes with the change of reagents...

 

[JayFish4004]

The level does not matter that much - look for stability. My DIY alk tester shows approx. 0.3DKH lower reading than Salifert (unless I stop Salifert titration at lavender colour reading)..

The more worrying thing is if DKH changes with the change of reagents...

Gotcha - I have experienced a bad batch of reagents with the nitrate high range and they sent a new lot over. I might pick up a salifert and another lot of alk reagent just to have some redundancy.

the current lot of alk reagent is brand new after finishing off the first lot, and there was no change between that switch so I feel pretty confident its not a bad lot of reagents, but ya never know.

Over all else I do believe it is stable and my ph is a steady 8.3

 

[JayFish4004]

Not impossible at all depending on the timeframe you are talking about.

If in a brand new tank for example you have 8.0 alk and your WC water is always 8.0 then if your dkh drops by .15 every week and you do a weekly 15% water change then the end result is each week your alk will drop by approximately .10 initially and then less as the weeks go on (because the WC becomes increasingly higher alk relative to tank water) until you get to around 7.0 and it would stabilize.

Of course usually the salt mix never is always exactly the same alk and consumption rarely always stays exactly the same, but it shows that over time if you have .3dkh drop biweekly (.15dkh/week) and you do a 15% change weekly then you will end up with an alk around 7 after several weeks. Again this is all else staying the same which it rarely does. 7 vs 6.8 is easily testing MOE (or variation in your salt mix or consumption assumptions).

To your last point - am I doing my tank a disservice using a salt mix that is 8 alk that would eventually level out to 7? Should I be going to a salt that mixes at 9 so it will stabilize at 8? I currently use AccuraSea1 from Two Little Fishies.

I want to avoid dosing at all costs and I also don’t want to move to a higher alk salt if it ends up creating too much instability without dosing.

 

[mdb_talon]

@JayFish4004 If your goal is a dkh of 8 and you dont want to dose (which is completely understandable) then ideally you will want a salt mix that more like 9-10dkh if doing weekly 15% changes.

For example if your tank starts at 8dkh and consumption is .15dkh per week and you use a 9dkh salt then at the end of the week you will be at 7.85dkh before the WC and back to 8dkh after the water change. The spike is very minimal and keeps you stable overall.

Of course the problem with this logic is that alkalinity uptake rarely remains stable so it wont just always end up that perfect. A higher dkh salt though would definitely help though. Eventually if your coral is growing well and you have stony corals and or a lot of coralline you may be left with no choice but dosing if you want to keep it stable (though this could just mean using kalk in topoff water for example does not necessarily mean you need a dosing pump)

 

[gbroadbridge]

The level does not matter that much - look for stability. My DIY alk tester shows approx. 0.3DKH lower reading than Salifert (unless I stop Salifert titration at lavender colour reading)..

The more worrying thing is if DKH changes with the change of reagents...

I find it useful when coming to the end of a bottle of Hanna Alk reagent to do a test at the same time with the old bottle and from the new to determine the offset between the bottles.

Hanna thoughtfully give you a 30ml bottle for 25 test kit, so you get the comparison test for free

A somewhat better option is to use the procedure detailed below to provide a stable baseline.
In fact I use this method almost exclusively as it works out much cheaper and is consistent.

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

 

[Borat]

I find it useful when coming to the end of a bottle of Hanna Alk reagent to do a test at the same time with the old bottle and from the new to determine the offset between the bottles.

Hanna thoughtfully give you a 30ml bottle for 25 test kit, so you get the comparison test for free

A somewhat better option is to use the procedure detailed below to provide a stable baseline.
In fact I use this method almost exclusively as it works out much cheaper and is consistent.

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

It's not as simple as that - for that "method" to work accurately, you need to fulfill 3 conditions:
- accurate PH probe calibration around 4.0PH and,
- accurate 0.1N acid mix
- accurate measurement of acid volume

In reality - you have potential inaccuracies coming from all 3 sources, but my estimates were that with a good PH probe - you should be able to measure up to 0.1DKH precision..

 

[gbroadbridge]

It's not as simple as that - for that "method" to work accurately, you need to fulfill 3 conditions:
- accurate PH probe calibration around 4.0PH and,
- accurate 0.1N acid mix
- accurate measurement of acid volume

In reality - you have potential inaccuracies coming from all 3 sources, but my estimates were that with a good PH probe - you should be able to measure up to 0.1DKH precision..

Yes, I think I achieve somewhat slightly better than that

 

[Borat]

Yes, I think I achieve somewhat slightly better than that

How do you know that your acid concentration is accurate?

 

[gbroadbridge]

How do you know that your acid concentration is accurate?

At some point there is a level of trust

 

[JimWelsh]

How do you know that your acid concentration is accurate?

With a sodium carbonate primary standard.

 

[Lavey29]

Makes sense - Ill bring a sample into my LFS this weekend for a sanity check. My gut is leaning towards the ATI test being off but I also don’t want to assume that without knowing for certain.

I had differences also with my Hanna checkers at the ATI test. The biggest was calcium. ATI showed 384 and Hanna 474.