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View Full Version : Different test kits, different reading, which is right?


Chihuahua6
02/12/2013, 01:32 PM
I have read several posts recently where the person tested with several different test kits and got completely different readings. for example calcium of 450 with one kit, 420 with another and 385 with the another.

Which kit should we believe?

I have API for alkalinity and Salifert for calcium. I really do not want to buy two other kits for each just to compare the different numbers.

How can test kits be so off?

Chihuahua6
02/12/2013, 01:35 PM
Here is what Signal151 posted on one of his threads for calcium:
- ELOS: 440
- HANNA: 409
- Red Sea Pro: 360

BrklynArch
02/12/2013, 01:36 PM
I usually do a few tests and average the results. I've tried a bunch of different test kits and I find that almost all of them have there own issues. Because of all the inconsistencies I've developed test kit trust issues.
I use elos Red Sea and salifert and a couple of the Hanna checkers for phosphate and alk the calcium checker is useless...I always get diff # between them. I usually take the average and use that

For Alk - Elos: quick and easy to do but consistantly @ 1dkh lower then others
Hanna: easy to do and generally consistent.
Red sea: also easy to do, and pretty consistent.

For Calcium - Elos: I usually just do test A, also pretty consistent
Red Sea: pretty good, easy to do and consistent
Hanna: stopped using it a while ago, very inconsistent the testing procedure
is very delicate and finicky. Way more trouble than its worth

For Mag - Red Sea: pretty good, easy to do and generally consistent. Test takes a little
time to do helps to have a stopwatch
Salifert: quicker than the Red Sea and seems consistent

For Nitrate- Salifert: it's ok, I don't really like any of the color comparing type tests.
Elos: also ok ... again the color comparing charts suck

For Phos- Hanna checker : its very good works well

bnumair
02/12/2013, 01:53 PM
i only use 1 test kit for one metal. this way i dont get into the problem ur in.
i also do multiple tests and average the results if different. i get higher end test kits like hanna checker salifert and red sea. i dont use API or cheap kits unless its for something like ammonia and nitrites.

disc1
02/12/2013, 02:36 PM
Which one is right? Who knows? All of those numbers sound like they are within the normal testing noise.

But to find out which one is closer to the real value you need to run the tests on a sample with a known level. Unless you have a standard to compare them to all anyone can do is guess.

cracker642
02/12/2013, 02:46 PM
I guess I'm sol I've been using api my whole tank life what's best site to get the good test kits and which test are the most important test to run I think api has a reef test kit and master reef test kit

PrangeWay
02/12/2013, 03:00 PM
Pick a kit, and aim for consistency with that brand/process.

You can drive yourself insane trying to find the "right" number. When I ran a Zeo/SPS tank I had 5 alk kits (LaMotte, API, Elos, Salifert, Red Sea) and normally 3 would at least be close to each other and that was "right". Do not let this happen to you. It was insane :)

disc1
02/12/2013, 03:03 PM
I guess I'm sol I've been using api my whole tank life what's best site to get the good test kits and which test are the most important test to run I think api has a reef test kit and master reef test kit

How are your animals doing? That's the more important question. I don't care if my calcium test reads "Triangle" instead of a number, as long as I know that my animals like a Triangle worth of calcium.

As an example, I have been running on an old salifert magnesium kit for some time. I left the bottle open once and the titrant partially evaporated. So now when I check my tank my magnesium reads something like 900ppm. I know that is wrong, but I also know that is where that bunged up test should read when my animals are happy. So I keep on using it and targeting that 900 number. When I use it up and get a new test, I'll probably have to change my target number to jive with the new test.

Chihuahua6
02/12/2013, 04:26 PM
How are your animals doing? That's the more important question. I don't care if my calcium test reads "Triangle" instead of a number, as long as I know that my animals like a Triangle worth of calcium.


They are doing well. I have mostly softies but also a few lps, gsp and coralline covered rock. Coralline is spreading, lps is growing, softies and anemones are flourishing, shrimp are moulting.

I was using Instant Ocean which is known to be a bit on the low side with calcium and magnesium so I started dosing two part after a short time. I noticed that I had to add more part two for alkalinity than part one for calcium. I'm thinking that maybe it was just the two different test kits showing the slightly low alkalinity?

I think I will just dose both parts equally for now since I just did a 65% water change after a tank upgrade and added a bit of two part to the new water (used Instant Ocean salt.)

bertoni
02/12/2013, 10:05 PM
I suspect the different dosing rates are due to testing noise or water changes, but the solutions could be a bit off, too. I think your plan of action is fine. :)

Spyderturbo007
02/13/2013, 08:50 AM
I have run the Red Sea Pro test kit against our ICP here at work and it is spot on.

nanotank
02/13/2013, 11:09 AM
I have recently switched to all red sea pro test kits. I find them better then most I have used in the past. I like elos also but for po4 hanna is the way to go. I don't use the checker version but the old school larger one.

Signal151
02/13/2013, 08:10 PM
Hi Amanda,

After all is said and done I think PrangWay said it best. Pick a kit and aim for consistency. Don't worry about the rest. Consistency is the key to a thriving tank, even if you're off a bit from actual values.

As for how can test kits vary so much? There are a lot of variables. Drop sizes, drop size consistency, and the method of reading colors are big variables. May times you can run a test twice with the same test kit and get a different result. In my opinion, the better designed the kit, the lower the difference in result from back to back tests of the same sample. Even if used in different lighting.

For calcium I don't think you're going to do better than the Salifert kit you already have. The only drawback to the API alkalinity kit, if it's anything like my old API kit, is that it only has a precision of 1dKH. More advanced tests such as the Hanna will have a precision of 0.1dKH. Thus you'll be able to monitor a change in you dKH from 8.2 to say... 8.6. However, if that level of precision isn't important to you, and honestly, it's not necessary, then the API is perfectly fine.

Ron Reefman
02/14/2013, 07:15 AM
Amanda, our local club did a 'test your test kit' meeting and the basic results were that there is very little consistancy between kits and users (about 30 testers). API, Salifert and Red Sea were the most common kits. In one test they may all be close but 1 or 2 people would have repeatable outlier numbers, sometimes for one maker of kit and sometime not. It was a real mixed bag of results. But for the most part, all the kits were in the same ballpark and even though API gets a bad rap at this website more often than not, they were right in the hunt with Red Sea and Salifert.