Is there a sweet spot for when to take ICP test? IE - Before or after water change?

[Ironic_Water]

I'm about to do my very first ICP test (Fauna Marin) and send it over to ol' Deutschland soon.

I'm wondering when you take your samples for the test? I'm recovering from a massive hair algae bloom which cratered my nutrients, and I've been doing more than the usual amount of water changes just in case.

My fear is that if I do the test after a partial water change, the test may falsely show my tank is more balanced than it is. But on the other hand it could show problems that persists even right after a water change... Hmm... I'm probably overthinking this.

I don't know, what do you guys think?

 

[KrisReef]

I think after a series of water changes the "balance" that the tank is working towards will be hidden by the flurry of water changes. You should know what your tanks parameters are now. If you take a test now you can compare those results with what you are getting with your test kits along with other elements that we can't test for without ICP.

Once you have the first test, keep doing your normal routine and send in a second one and then you will have an idea of what has happened between tests. Having one test provides one point, having two may show trends, and having 3 gives you the numbers to plot to see if there are trends, or just variations over time or in testing itself.

Test your water and send in a sample to see how your test results compare with ICP. Point 1. HTH.

 

[irischan]

i think it is better to test just before water change. if the result is bad, it means you may consider more a bit more frequent/heavy water change practice.

 

[Dan_P]

I'm about to do my very first ICP test (Fauna Marin) and send it over to ol' Deutschland soon.

I'm wondering when you take your samples for the test? I'm recovering from a massive hair algae bloom which cratered my nutrients, and I've been doing more than the usual amount of water changes just in case.

My fear is that if I do the test after a partial water change, the test may falsely show my tank is more balanced than it is. But on the other hand it could show problems that persists even right after a water change... Hmm... I'm probably overthinking this.

I don't know, what do you guys think?

What size water change are you doing?

A 10% water change increases the concentration of trace elements by the amount similar to the error in the ICP measurement. With an ICP measurement you can find big problems but won’t be able to fine tune anything.

 

[Jamie814]

Water changes help replenish missing or low elements. If you pull a sample for icp first, then do a water change your icp test results are not going to be as true/accurate to your current water parameters.

 

[EricR]

i think it is better to test just before water change. if the result is bad, it means you may consider more a bit more frequent/heavy water change practice.

My use of ICP is really for long-term -- is something depleting or getting oversaturated over a long period of time.
On that note, seems like it doesn't matter but I always do the same = late in my water change cycle (meaning, haven't changed water recently).

 

[mrpontiac80]

After seeing some aquabiomics test results from reefbum’s podcast, I think 24-48 hrs after a water change is ideal. Also, when I do an icp, I test everything manually and record the results. That way I can compare my tests with icp results.

 

[Reefahholic]

Always wait 48 hrs after last water change and before any daily dosing or feeds.

If you’re cycling a system wait until the cycle is complete and then send the ICP.

 

[Reefahholic]

With an ICP measurement you can find big problems but won’t be able to fine tune anything.

Why do you think that? Are you talking about due to the water change/s or fine tuning the ICP results in general.

 

[gbroadbridge]

I'm about to do my very first ICP test (Fauna Marin) and send it over to ol' Deutschland soon.

I'm wondering when you take your samples for the test? I'm recovering from a massive hair algae bloom which cratered my nutrients, and I've been doing more than the usual amount of water changes just in case.

My fear is that if I do the test after a partial water change, the test may falsely show my tank is more balanced than it is. But on the other hand it could show problems that persists even right after a water change... Hmm... I'm probably overthinking this.

I don't know, what do you guys think?

It makes no difference.

A 10% WC will be within the ICP LOD and/or accuracy anyway.

Don't forget that by the time you have the results there will be differences also due to biological action/consumption in the tank.

 

[Reefahholic]

Don't forget that by the time you have the results there will be differences also due to biological action/consumption in the tank.

If the system is stable this doesn’t matter much. If elements are depleted, they will need to be dosed up regardless if it’s been a week or a month. You never see depleted elements come back into normal range w/o dosing them back in some form.

 

[ingchr1]

I will draw an ICP sample halfway between water changes. I do a water change every two weeks, so I draw the sample 7 days after the water change. I will also not send in a sample unless my salinity and alkalinity are where I want them to be. If I have made changes to the amount of TM A- and K+ I am dosing, I wait until I have gone through at least a gallon of two part (I add the elements to the two part). For my tank, that's about three months. I only send in a couple of ICP samples a year.

 

[Dan_P]

Why do you think that? Are you talking about due to the water change/s or fine tuning the ICP results in general.

I am thinking standard deviation.

When two measurements differ by 5%, say one in April and the second in May, and the standard deviation of the measurement is 5%, I cannot be confident that the difference between the April and May samples is real or noise in the data. If there is a 20% difference between April and May samples, I feel more confident in claiming that a difference exists. In this situation, I might consider making an adjust based on the measurement. In the first situation, I would not make an adjustment. So, what is the standard deviation of each element concentration measured by an ICP vendor?

Nobody knows. ICP vendors do not tell me the standard deviation of their measurements., I have to look for evidence for the size of variability there might be, and estimate a standard deviation. The data I have seen suggests that we can have very high confidence in results of elements measured to be above 1 ppm and we should have little confidence in the results below 1 ppb. Between 1 ppm and 1 ppb we might have high confidence that the element was detected and that the concentration reported might be regarded as an estimate with a standard deviation of 10-20%. And this is why I said use ICP to look for big issues, big concentration differences month to month, the presence v absence of toxic metals, but not making small tweaks to any one element. The likely standard deviation of ICP measurements does not justify making adjustments based on small differences but would when differences are large. Adding to the uncertainty in ICP measurements is that today’s standard deviation may not be the same as last month’s. To make my life simple, I just assume it is approximately the same.

 

[Reefahholic]

I have to look for evidence for the size of variability there might be, and estimate a standard deviation.

I think you might be a little too cautious. At some point you have to live a little. The deviation is not as much as you might think if using a quality lab like OCEAMO, and not every element will be dangerous if overdosed even at what you might consider a significant deviation. IMO, it’s more detrimental to try and play it safe by not dosing some of these elements because of fear. Many of them are extremely important, and used for so many functions and processes by literally everything in our reefs.

The data I have seen suggests that we can have very high confidence in results of elements measured to be above 1 ppm and we should have little confidence in the results below 1 ppb. Between 1 ppm and 1 ppb we might have high confidence that the element was detected and that the concentration reported might be regarded as an estimate with a standard deviation of 10-20%.

Which labs do you have data from?

I have very strong confidence in values under 1 ug/L with OCEAMO’s MS.

If you’re sending OES you shouldn’t have much confidence for most ultra trace elements. Some obviously have better sensitivity than others, but not enough for me. Like you mentioned, it’s fine for major elements. See more about that in my comment below.

I can tell you firsthand that OCEAMO’s ICP-MS will get you down to a detection limit of 0.05 ug/L or better for almost all the elements which is well below their targets for all ultra trace. Why would I say that? Because I see it daily/monthly, and have been for a long time now. I see elements moving by 0.1-0.2 ug/L based on my dose corrections. This can’t be done with any OES.

The likely standard deviation of ICP measurements does not justify making adjustments based on small differences but would when differences are large.

Only if you’re sending OES. It’s ok for Major elements and some traces that have higher target ranges like Ba, F, I and Mo.

OCEAMO ICP-MS gives you the ability to tweak elements with targets down under 1 ug/L “easily” and “accurately.” I have the data to prove that. We can compare my test results to other test results, and determine who’s hitting target values closer. The deviation isn’t as much as most think it is, and if it were, I should not be able to hit target ranges under 1 ug/L accurately or consistently. Just let me when you want to compare my results to anybody you choose. We can let the data talk.

 

[Dan_P]

I think you might be a little too cautious. At some point you have to live a little. The deviation is not as much as you might think if using a quality lab like OCEAMO, and not every element will be dangerous if overdosed even at what you might consider a significant deviation. IMO, it’s more detrimental to try and play it safe by not dosing some of these elements because of fear. Many of them are extremely important, and used for so many functions and processes by literally everything in our reefs.




Which labs do you have data from?

I have very strong confidence in values under 1 ug/L with OCEAMO’s MS.

If you’re sending OES you shouldn’t have much confidence for most ultra trace elements. Some obviously have better sensitivity than others, but not enough for me. Like you mentioned, it’s fine for major elements. See more about that in my comment below.

I can tell you firsthand that OCEAMO’s ICP-MS will get you down to a detection limit of 0.05 ug/L or better for almost all the elements which is well below their targets for all ultra trace. Why would I say that? Because I see it daily/monthly, and have been for a long time now. I see elements moving by 0.1-0.2 ug/L based on my dose corrections. This can’t be done with any OES.




Only if you’re sending OES. It’s ok for Major elements and some traces that have higher target ranges like Ba, F, I and Mo.

OCEAMO ICP-MS gives you the ability to tweak elements with targets down under 1 ug/L “easily” and “accurately.” I have the data to prove that. We can compare my test results to other test results, and determine who’s hitting target values closer. The deviation isn’t as much as most think it is, and if it were, I should not be able to hit target ranges under 1 ug/L accurately or consistently. Just let me when you want to compare my results to anybody you choose. We can let the data talk.

Your opinion about OCEAMO seems to rest solely on belief rather than data. For hobby purposes that’s OK because there seems to be very little science behind the need for tight control of element concentrations. An analytical method of unknown accuracy and precision is a method fit for such a purpose.

 

[Reefahholic]

Your opinion about OCEAMO seems to rest solely on belief rather than data.

These are not opinions or beliefs. This is data. What I’m stating rests solely on experience using ICP-MS, and the data itself. We’ve been controlling elements within our target ranges (that are typically between 0.35 - 0.7 ug/L for Ultra Trace elements) for a long time now. Being able to hit targets within a 0.35 ug/L window is very precise. It’s much more precise than these large fluctuations you’re talking about. We’re doing it monthly too, and if I were to move to biweekly it would be even tighter. If that’s not precision then I don’t know what is. There’s too many people wasting money on crappy labs sending out OES and wondering why they’re ultra trace are coming back as “u.” or “n.n. “