Which Liquid Test Kits Are Most Accurate?

Well I must confess that with over 2 years in the hobby and great equipment from reputable manufacturers such as Tunze and Precision Marine I regret to inform everyone that I was tempted by the low prices of the Aquarium Pharmaceuticals Liquid Test Kits. (Yes I know sham on me). Well it almost 2008 and I've stepped up almost every other aspect of my Reef Keeping Hobby and now it time to do so again. My question is this. Despite the price which liquid test kit for various chemicals such as Calcium, Magnesium, phosphates, etc do you consider the most efficient and the most accurate? I've been considering such liquid test kits from LaMotte and Elos but would love to get everyone elses thoughts on this matter.

The API kits seem to work OK for me, though I havent actually tested it against anything else. And I don't test that often either. I did just get a electronic ph/ORP meter for christmas, so at least I can check on ph easily now and make sure my water change matches. Of course I use a refractometer for salinity, but for calcium, phosphate, nitrite, nitrate, and ammonia use the API tests.

i use API test kits too. they work fine for me.

I have always been happy with Salifert.

As far as accurate I cant really comment with out a laboratory grade kit to compare to. Any one have one I can use? :D

I like Salifert mainly because I think they are easier to use. Not a lot of experience with other kits, I've used API (not bad, used the freshwater kit for my cichlid tank) and Instant Ocean (PITA really..hard to open the little packets, very messy)

Don't know how you would test the accuracy. I saw a thread on reef central where this guy was using a handheld Phosphate probe to see how fast a phosban reactor was lowering his PO4. It'd be interesting to test a kit vs. the probe.

Here's the link: GFO (Phosban) Just how good is it?? (http://www.reefcentral.com/forums/showthread.php?s=&threadid=1182318)

I agree there is no way to determine the most accurate without using laboratory grade tests. I worked in a lab doing water chemistry tests for several years, too bad I still don't or we could run some comparisons. I wish there were more reviews like this Advanced Aquarist's Online Magazine - Product Review: Alkalinity Test Kit Showdown (http://www.advancedaquarist.com/2007/8/review) to help us determine which kits are accurate. Salifert kits have an expiration date on reagents. I really like my SeaChem Reef Status Mg kit. It works more like a laboratory test.

I have a Colorimeter by Lamotte and I've tested many of the test kits against the Colorimeter. Salifert was almost dead on. Fast Test was close on all but the Phosphate. Although it did register that water contained phosphate, when it did, the amount it registered with a bit higher than the Colorimeter. The API kits were also close...not dead on, but in the general vacinity. I'm going to be trying out the Elos soon. I'll post results for that when I get them.

I also use API and like them alot. There inexpensive and pretty accurate.

I have a Colorimeter by Lamotte and I've tested many of the test kits against the Colorimeter. Salifert was almost dead on. Fast Test was close on all but the Phosphate. Although it did register that water contained phosphate, when it did, the amount it registered with a bit higher than the Colorimeter. The API kits were also close...not dead on, but in the general vacinity. I'm going to be trying out the Elos soon. I'll post results for that when I get them.That is very helpful, I'll look forward to ongoing reports!

I have a Colorimeter by Lamotte and I've tested many of the test kits against the Colorimeter. ... I'm going to be trying out the Elos soon. I'll post results for that when I get them.

I do not doubt that the Elos kits are accurate, but the Ca and Alk kits have very low resolution compared to Salifert. (Each drop in the Alk kit is 1 dKH, each drop in the Elos Ca kit is 25ppm!) Please see my informal Alk comparison (http://www.talkingreef.com/forums/member-tank-projects/5327-rroselavy-s-55g-2.html#post70731). You can increase the Elos resolution by using twice the amount of SW, but you would have to triple the amount of SW to approximate the much smaller drop size of the respective Salifert kits (all due to those precision Salifert syringe tips). You would burn through a lot of Elos reagent, and those kits aren't cheap.

In the end, the Elos Ca & KH kits are nice (probably fine for casual use), but - low resolution obscures its accuracy. I emailed the Elos rep (Jesse Sira - fantastic guy), who said that Elos was going to address this issue with a few kits shortly (around Interzoo). IMHO, Elos simply needs more precise droppers in these kits.

BTW: Jesse had told me that they already increased the resolution on the Elos PO4 kit, which is supposed to be an excellent kit. MD is carrying the new version of these kits now.

I assume that Lamotte is the benchmark, but my experience (and thus my vote) is based on Salifert (Ca, Mg, KH, NO3, PO4) , Elos (Ca, KH) and Red Sea "Marine Lab" kit.

First, hobby test kits are not lab grade test kits. Most have an accuracy between 3% & 10% of the actual value. So if you are using Salifert because your results state 3.54, Habib has got you fooled. The actual sample will be anywhere from 3.19 to 3.89. So what would it matter if it says 3.25 or 3.5 or 3.75? or 3.0 or 4.0 ?

I have found Salifert Alk to be the least accurate anywhere from 10, 20, and even 30% off. I have found API ALK to be accurate enough as it is at most 1.0 dkh higher than actual. Salifert Calcium was just as inconsistent. I have found his Mag to be close enough. ELOS Calcium is the most accurate kit that I have ever used to date.

First, hobby test kits are not lab grade test kits. Most have an accuracy between 3% & 10% of the actual value. So if you are using Salifert because your results state 3.54, Habib has got you fooled. The actual sample will be anywhere from 3.19 to 3.89. So what would it matter if it says 3.25 or 3.5 or 3.75? or 3.0 or 4.0 ?

Hey Ralph. What I am trying to say is that a lack of resolution can amplify kit inaccuracy, and that I would prefer that a reasonably accurate hobby kit result was not marred by a lack of resolution. More precisely, that the resolution error should be no greater than the reagent error. Feel free to correct me, as I have no expertise in these matters.

Lets use the Elos KH titration test kit as an example, and assume that it is (however unlikely) always dead-accurate. The resolution of the kit is 1 dKH (1 drop of reagent per dKH). If my real dKH is 7.2, I will not see the titration change until I put in the 8th drop of reagent. My result for this dKH would always be offset by 9.5%, but my result of 8.0 dKH would be consistent.

Now lets say that my sample is actually 7.0 dKH, and there is a nominal test kit accuracy error of +3%. My kit would measure that 7.0 dKH sample as 8.0 dkH, which represents an overall error of 14%.

If the Elos KH titration drops were one-third the size (like the Salifert kits), my test result would have been approximately 7.3, or 4% off the sample. Making the drops smaller does not seem that expensive to me, especially after having seen and used the Salifert syringes with the precision tip. This is not to say that Salifert's Alk/KH kits are necessarily accurate, but that resolution is not the limiting factor in their overall accuracy.

Accepting the fact that Hobby kits are 3%-10% in terms of reagent accuracy does not mean that we have to allow the error to be amplified (in my hypothetical example of a 3% error to 14% error) by poor resolution.

The difference between 7.0 dKH and 8.0 dKH may be of little concern to most Hobbyists, and pehaps rightly so. I see 7.0 dKH as on the threshold, while 8.0 dKH is within a margin of comfort. This probably just reflects my inexperience in the hobby.

And I realize that consistency is more generally valued over accuracy.

Thanks for the article. It will be interesting to see the Part II. I do not agree with their assumption that "the mean is an accurate representation of the true value", but it is probably reasonably close.

The exchange about the Ca and Mg Ions was also interesting. I suppose we just aim for values that we know work for corals and maintain those levels as consistently as we can.

ok,gotcha!

Our club recently performed a test on different test kits and here are the results. This was phase one and we are planning a more comprehensive study real soon.

Here's the write-up of the results. (http://www.dfwmas.org/pdf_files/Test%20Kit%20Analysis.pdf)

Great information, thanks! Here is another great comparison Advanced Aquarist's Online Magazine - Product Review: Alkalinity Test Kit Showdown (http://www.advancedaquarist.com/2007/8/review).

IME, there isn't a 'best' brand for any particular parameter.

For kH - I like ELOS & API for quick checks. They're easy to count drops and fast. When I sit down to check monthly, I use the LaMotte. It has better resolution. All 3 kits match each other. SeaCehm's is decent, but I don't like readings in meq/L (not accurate imo, I DO care about a difference in 1 degree dkH), and I dislike their little trays.

For Ca, again, ELOS, API & LaMotte. The Lamotte is a pain, but it's accurate. I prefer ELOS for Ca, even though it's a bit more $ than API, I think the quality is higher.

Mg, once again, ELOS. Salifert's kit is also very easy. SeaChem's is more accurate (resolution wise) than ELOS, but it is a pain and time consuming to use. I''l go elos or Sali any day for Mg - for Mg I don't really need to 10ppm resolution of SeaChem or Sali. I just want to know that it's over 1250, preferably 1300, and under 1400.

PO4 is, if you can't get a hanna, DD Merck hands down, imo. I've used Salifert's PO4 and SeaChem's, neither of which I like at all.