A discussion about test kits, water parameters and what lays between them...

[Ozcha]

Hi all,
I always wondered about the accuracy of the test kits we're all using.
Every-time I read a post regarding water parameters, the question / suggestion to calibrate the digital instrument / check with a different kind of kit, pops out.
After a long discussion, a known option thrown to the air saying that there's no accurate testing kit that is accessible to the hobbyists.
Nothing is accurate when we need to measure the parameters by their colors...
In some test kits, a single drop can make the difference (MG, CA, ALK, etc.)
some says that Refractometers are not that accurate as some of us used to think.

My question is obvious but I'll ask it anyway...

How can we know the exact parameters of our water?
How can we maintain a long last stable environment based on the above problem?
Do we have an option? one that'll give us all the info we're looking for?

Thanks all, and hopefully, this thread will give us some usefull options...

Oz

[Randy Holmes-Farley]

Expensive lab tests are an option, but luckily, for most situations, extensive testing is not necessary. Our tanks are often a lot more forgiving than we think about some of the basic tests.

There are few things I regularly test. Those are pH and salinity and temperature.

Other things I test much less frequently.

For alkalinity, i use a DIY which I have high confidence in, but which you may not easily be able to buy the acid standard needed.

[HighlandReefer]

We do have a range for each parameter to work with.

Alk: 7-11 dKH
calcium: 385-450
mag: 1250 - 1350

In addition hobbyists have pushed these limits much higher for each of the big three parameters without apparent problems. If you reduce the individual parameters lower than the recommended levels, this seems to lead to problems.

I shoot for the center of the recommended parameters since test kits can be off some, but are close enough when you aim for the middle. ;)

[Ozcha]

In normal days, I would be satisfied with everything you wrote, BUT... just a day ago I went to a friend of mine after complaining he has a problem with his reef tank...
We tested his parameters over and over again with Salifert test kits (mine and his), 2 refractometers (2 manufacturers), Martini PO4 digital test kit, and every time we got a different values (mainly with PO4).
While reading some posts here, I saw that there's a "few" threads indicating a known issue and the conclusion is that "nothing is certain (except death)" and there's no real accurate solution for water testing.

I know there's a large range for each parameter, but with PO4, there's a big difference between 0.01 to 0.10 (shocking, I know).

[HighlandReefer]

Every time I test my tank for phosphate both the Salifert and the Hach PO-19 phosphate kit test zero. If they were above zero, I would either add more GFO or replace it more frequently. IMHO, the phosphate test kits are only good to make sure you have a zero reading. ;)

[Ozcha]

HighlandReefer,
What I didn't mention is while the digital PO4 indicated 0.01 or 0.1,
The salifert test kit showed 0.
So, zero value with the chemical test kits, indicates nothing (from my experience).

[Randy Holmes-Farley]

The Hach PO-19 phosphate kit can unquestionably distinguish 0.1 from 0 ppm. I think it has a resolution of about 0.03 ppm in my hands. Meaning that I can just distinguish 0.03 ppm from 0 ppm. :)

[HighlandReefer]

I was using the recommended guidline of keeping your phosphate level below 0.03 ppm. The Salifert kit does a good job reading zero when the level is below 0.03 in my experience when comparing it to the Hach PO-19.

If you want your phosphate level lower, then problems start with available hobby grade test kits & meters which have a margin of error around (+or -) 0.04 ppm. Even colorimeters have margin of error between (+ or -) 0.01 - 0.02 ppm & can't detect below 0.01. So I don't see any real benefit of even using a colorimeter unless there are economical ways of detecting phosphate down to natural sea water levels around 0.005 ppm phosphate.

IMHO, using the Hach PO-19 phosphate kit & making sure you keep a zero reading is the most economical way for maintaining phosphate levels. ;)

[balberth]

My feeling about this is that one needs to cultivate a relaxed attitude towards measuring parameters in order to avoid tearing one's hair out. Tests are but one part of determining the cause of any reef tank problem, and they may be able to give you early warning of trouble brewing, but if you rely on the color of a chemical concoction to tell you if your animals are healthy, there will be no end to your worries.

We have thermometers and refractometers to measure basic parameters that we can set. I have two digital thermometers that I periodically check against each other, and a NIST traceable glass thermometer I occasionally use to verify. I'm pretty sure of the temperature of my tank. I calibrate my refractometer to a 35ppm reference, and periodically check that it remains calibrated with that reference. I also occasionally do a sanity check with a hydrometer. I'm pretty sure of my salinity.

Then we have some titration tests to measure things that should be correct in the original mixed salt water, but which degrade over time. We supplement these things - calcium, alkalinity and to some extent magnesium - either through additives or through water changes. I use Salifert tests, and I'm reasonably sure that my readings are correct because I trust the methodology of the tests as far as I understand them, I use fresh kits, and because the readings make some sort of sense internally. The fact that these kits appear to use syringes for ALL critical measurements makes me more sure of the results. And I target moderate values for these parameters, just in case. The tests do not have to be very accurate to keep my parameters within acceptable regions, and do seem repeatable.

Then we have parameters we test for things we don't want in the tank. Phosphorus and Nitrate, for instance. These tests tend to be colorimetric tests, which rely not only of relatively precise measurement of the reagents but also our ability to match colors in an unregulated environment. I use these tests to tell me if I have a none, a little, or a lot of the measured substance, but I would not trust them to tell me more than this. Generally, the goal for these substances should be zero on hobbyist level test equipment, at least. We're not trying to hit a target, we're trying to minimize the level, so these tests are accurate enough to tell me if I am in big trouble or not.

Then we have pH. Which should be above 8 or so. And which we generally control for by adjusting alkalinity, but we already measure that. I do not trust the colorimetric tests for this, so I have a pH meter which I don't trust either. Because it seems that every time I recalibrate it I end up with a slightly different number. I tend not to worry about this parameter too much because I am assured that if I am controlling my other parameters reasonably well, it doesn't actually matter that much...

I try to remember to run tests and record the results weekly. But I look much more at algae growth in my tank, polyp expansion, coral color - in my experience, those things will tell you if you have a problem ... a test may tell you more clearly what's causing the problem, especially if you have a long history with which you can compare ... but it's only part of finding and solving a problem.

[Ozcha]

Thanks all, for your answers...
balberth - I enjoyed reading your detailed opinion. It really does make sense and it gave me a lot of things to think about... keeping me in the right proportion.

BTW, Excuse my ignorance, but what is "Hach PO-19" you keep writing about?

Thanks again,

[HighlandReefer]

http://www.hach.com/hc/search.product.details.invoker/PackagingCode=224800/NewLinkLabel=Phosphorus,+Orthophosphate+(reactive)+Test+Kit,+Model+PO-19,+Color+Disc,+100+tests

Once you buy the kit, refills are much cheaper. :)

[soulsigma]

My feeling about this is that one needs to cultivate a relaxed attitude towards measuring parameters in order to avoid tearing one's hair out. Tests are but one part of determining the cause of any reef tank problem, and they may be able to give you early warning of trouble brewing, but if you rely on the color of a chemical concoction to tell you if your animals are healthy, there will be no end to your worries.

We have thermometers and refractometers to measure basic parameters that we can set. I have two digital thermometers that I periodically check against each other, and a NIST traceable glass thermometer I occasionally use to verify. I'm pretty sure of the temperature of my tank. I calibrate my refractometer to a 35ppm reference, and periodically check that it remains calibrated with that reference. I also occasionally do a sanity check with a hydrometer. I'm pretty sure of my salinity.

Then we have some titration tests to measure things that should be correct in the original mixed salt water, but which degrade over time. We supplement these things - calcium, alkalinity and to some extent magnesium - either through additives or through water changes. I use Salifert tests, and I'm reasonably sure that my readings are correct because I trust the methodology of the tests as far as I understand them, I use fresh kits, and because the readings make some sort of sense internally. The fact that these kits appear to use syringes for ALL critical measurements makes me more sure of the results. And I target moderate values for these parameters, just in case. The tests do not have to be very accurate to keep my parameters within acceptable regions, and do seem repeatable.

Then we have parameters we test for things we don't want in the tank. Phosphorus and Nitrate, for instance. These tests tend to be colorimetric tests, which rely not only of relatively precise measurement of the reagents but also our ability to match colors in an unregulated environment. I use these tests to tell me if I have a none, a little, or a lot of the measured substance, but I would not trust them to tell me more than this. Generally, the goal for these substances should be zero on hobbyist level test equipment, at least. We're not trying to hit a target, we're trying to minimize the level, so these tests are accurate enough to tell me if I am in big trouble or not.

Then we have pH. Which should be above 8 or so. And which we generally control for by adjusting alkalinity, but we already measure that. I do not trust the colorimetric tests for this, so I have a pH meter which I don't trust either. Because it seems that every time I recalibrate it I end up with a slightly different number. I tend not to worry about this parameter too much because I am assured that if I am controlling my other parameters reasonably well, it doesn't actually matter that much...

I try to remember to run tests and record the results weekly. But I look much more at algae growth in my tank, polyp expansion, coral color - in my experience, those things will tell you if you have a problem ... a test may tell you more clearly what's causing the problem, especially if you have a long history with which you can compare ... but it's only part of finding and solving a problem.

A big THANK YOU for stating what has been said over and over that test kits are your guide and the appearance of your tank and animals are the real indicators. Watch you, study it and it will give you all the answers and the test kits will assist you in maintaing parameters or solving issues with off balance parameters.:fish2:

[Billybeau1]

Your eyes are the best test kit. If your tank looks good, it probably is.

Where have I heard that before. :D

Excellent points everyone. We fuss too much about an exact number in most cases when what we are really trying to maintain is stability.

I'll stick with the hobby grade kits. They work good enough for me. :)