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Old 02-15-2010, 02:09 AM   #1
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Observations on API test kits

I have been keeping fish for better than 20 years, but I've learned the most in the last year. I wanted to start this thread not really as a discussion, but more to just post some insight about my experiences with the Aquarium Pharmaceuticals Liquid Reagent test kits.

I have read plenty of threads questioning the accuracy of API kits and plenty of opinions about their reliability. So I wanted to start this thread in case anyone searches on the issue and wants to find out how to use them right, or find out if something is wrong with their test results.

First off, I want to say that I consider the API Master Test Kit to be the staple test kit for the average aquarist, especially the newbie. They're easy to use (and misuse, as I will discuss) and relatively inexpensive. It should be first on the list after tank, stand, light, lid, filter, substrate. Notice I did not say water or fish.

The #1 observation I have is a new one. I maintain some saltwater tanks and I own Salifert kits for some of those tests, because they are far more accurate - and more expensive. But several come with a 5mL syringe. I found out that the little glass vials that come with the API kit have varying levels of where the little white "5mL" line is placed, and it turns out that they really suck at accurately silkscreening that line at the actualy 5mL mark. So the first suggestion I have is to go to your local medical supply store (or pharmacy) and get yourself an accurate syringe and use that to take your water sample from the tank. It also saves your dipping and pouring out the vial to get close to that darn white line. Just ignore it!!

The #2 and likely more important observation is to follow the directions - EXACTLY. I always give the bottle a little shake, not matter which test it is, then hold the bottle upright and squeeze slightly to get any bubbles out of the dropper nozzle, and turn upside down while letting the pressure off so it sucks air in and clears the nozzle before squeezing. I squeeze very slowly so that the drops form uniform drop size, and I always hold the bottle completely vertical, just like the directions state. I have witnessed LFS employees holding the bottle horizontally and getting worthless results. FOLLOW THE DIRECTIONS. To expand on this, the most important test in which to follow directions, EXACTLY, is the Nitrate test. You MUST shake the #2 bottle, VERY vigorously, for at least 15 seconds (I go 30) to dissolve the solid that settles to the bottom (if you look closely at the drops, you can see the particles). This is critical for 2 reasons, the first being obvious, that you want the solid suspended, but secondly, if you don't do that on a regular basis, then down the road you're going to have too high of a solid to liquid ratio and eventually I expect your test reading to be completely worthless, either way too high or way too low, and how would you know? Continuing, after you add the #2 bottle drops you must cap and shake the vial for 1 minute (I always go exactly 1 minute). The caps they supply, IMO, don't create a very good seal, so for this part I take a tissue and fold it up, then wrap it around the top and put my thumb on the end and hold it tight and shake like crazy (CRAZY!!) and the tissue always ends up with some of the orange stuff on it. It's better than getting it all over your hands, and it doesn't affect the test to lose a bit of the solution, it's not about the quantity of solution, it's about the ratio of the reagents.

#3 - wait time. If it says wait 5 minutes and then observe, don't wait 10, or 3. Wait 5. A good example of this is the Phosphate test, it clouds up after 5 or 6 minutes and is worthless, but at 3 minutes it's fine.

#4 - Reading the result. This can be the hardest thing to do, especially on the pH kit. You just have to run enough tests with different results to be able to tell the difference. Sometimes, it helps to get a high reading on something, like Nitrate or Ammoina, then dilute the sample 50/50 with something known to be 0 (like bottled water) and test again to see the difference. But basically, if you hold the test tube firmly against the color card in moderate indoor lighting, it will look darker that if you hold it 1mm off the card. This can be particularly frustrating. You just have to use your best judgement. I hover it just above the color card, and sometimes against it, to get as close as I can, then I also stand it on end with the card flat in my hand and see which one looks as close as possible to the right color segment; usually I can get pretty close with the hovering and standing on card technique. Nitrate is the most difficult to read, but if you test right at 20ppm, the standing on the card method looks mainly red with an orange tint, and holding against the card you lose the tint, and when you hover it you can see it again.

#5 - Accuracy when levels are high. I have found that in the Ammonia and Nitrate test kits, any reading more than 1/2 way up the color card is virtually indistinguishable. 40ppm Nitrate looks the same as 160 ppm unless you have them side by side. So I get a 'control' sample (RO or bottled, and tested to verify 0 ppm) and use my syringe and suck up 1mL tank water and 4mL control water, and test that, then multiply by 5 (or 1/2 and 1/2 and x2, you get the idea). This works great. Don't try it on pH though, it's not the same. This works for Ammonia, Nitrite, Nitrate. It might work for a few others, like Phosphate and KH (use only RODI or distilled on KH dilution), but IMO you really need a Salifert kit if for KH (API one is worthless, trust me) and Phosphate is hard to read in both API and Salifert, although the Salifert kit is easier to read below 1ppm, so if it tests positive for Phos, just get ROWAphos, unless you don't care about algae. I have diluted for Nitrate test up to 16 to 1 until I have been able to get a reading under 30 ppm, I consider anything over 20 ppm (freshwater) or 40ppm (saltwater) to be unreliable due to color distinction on the color card.

The one test that I have found easiest to read is Nitrite when it's less than or equal to 1 ppm, and you can dilute for higher readings. The color change is very easy to distinguish. The only issue with that one is due to something called "amine interference" and only matters in a SW test. In a SW system, denitrification occurs in live rock or in a DSB. From what I understand, in this process, Nitrate is momentarily converted to Nitrite before being converted to Nitrogen gas, and leaving the system. If something is off (what, I don't know) this last conversion does not happen and the API kit may not pick up on it, and you could have Nitrite in your system that wouldn't show up. The only test kit that claims to be immune to amine interference is the Salifert kit. So this is a must have for the true SW aquarist. IMO, if you're running a SW tank, especially a reef tank, you should have Salifert kits to use to double check your readings occasionally, and the KH and Coral Calcium are a definite must have. You can't beat titration kits like the Salifert ones.

I haven't used the Coral Calcium or Copper API kits, but I wouldn't bother with the former and the latter I am guessing would be fine, because either you have copper or you don't, and that's all that matter.

As far as erroneous results, the most common one I come across (and it's not often) is in the Nitrate kit, and it's pretty random. If you test often enough and one doesn't seem right (always too low) then test again, and make sure you shake #2 enough.

The only other point I'll hit on is the issue with Prime. I've read thread either way on this one, but I've never encountered an erroneous reading after using Prime during a PWC. However, I never test right after a PWC, I always wait a while, usually a day, so that the water mixes enough. It is my understanding that Prime 'locks' ammonia and if you dose it enough (up to 5x label dosage) it will lock Nitrate also, but it is only temporary. In the case of Ammonia, from what I've read, it locks it and chloramine into a bio-available non-toxic form, so that it can still be utilized by nitrifying bacteria (i.e. it won't interrupt your cycle) but it won't harm your fish. So although you may test for high ammonia, you are actually seeing only Ammonium. Besides, almost every liquid reagent test kit tests for Total Ammonia Nitrogen (TAN) which is a combination of Ammonia (NH3, unionized) and Ammonium (NH4+, ionized), the ratio of which is a function of pH. For more on this, read this:

Aquaworld Aquarium - The Ammonia and pH Relationship

What it comes down to with regards to Prime, in my opinion, is user error. Hopefully I don't open up a huge firestorm on the issue, but that's the way I see it, although I don't really have any kind of study to back it up. It's just my experience that I've had zero problems with it.

Oh yeah, and if you're not using Prime, get with it. 1 mL treats 10g. 1 500ml bottle last you forever. I know one guy who has 2000g of Cichlid tanks and only uses 3 gallons per year of the stuff, and that's doing 50% PWCs regularly on all of them. Do the math.

So that's my rant! Hopefully this will help someone. Maybe if I get enough of a response out of it, with some other observations, comments, or corrections, it could become at article!!

Regards, and happy fish keeping,

aka Floyd R Turbo

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Old 02-15-2010, 07:53 AM   #2
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Nice write up.
I haven't used the Coral Calcium or Copper API kits, but I wouldn't bother with the former and the latter I am guessing would be fine, because either you have copper or you don't, and that's all that matter.
If you keep any coral with a hard skeleton, you should test for calcium.

A copper test kit is vital if you are treating for ich with a chelated copper product like Copper Safe. "Either you have copper or you don't, and that's all that matter" is not very accurate when treating parasites. You MUST maintain the proper copper level for the treatment to work.

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Old 02-15-2010, 08:10 AM   #3
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Very good addition, thank you! I fortunately enough have never had to use any kind of copper based treatment on my tanks. I guess where I got that statement from was in reading about SW, mainly buying a new tank and soaking it long enough to test for copper presence. Also was thinking of when treatment was done, removing the copper via carbon. Never thought about maintaining concentration level.

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Old 02-15-2010, 02:09 PM   #4
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Originally Posted by Floyd R Turbo View Post
The caps they supply, IMO, don't create a very good seal
I cut the thumb off a nitrile glove, works well as a finger condom for shaking up test vials sans the leaky lids.

Originally Posted by Floyd R Turbo View Post
get yourself an accurate syringe and use that to take your water sample
If you are both a cheapskate and a frequent tester, you can use your syringe or dropper to scale your tests, getting more per bottle. For example, if the instructions call for 10 drops and 5mL of water, you can use 6 drops and 3mL.

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Old 02-15-2010, 02:40 PM   #5
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Great write up. I bought the API pH when my meter quit working. I used a Salifert syringe to fill it with with 5ml of tnak water and I was surprised by how off it was from the white line. So I checked with several other syringes (Lamotte test kit, other Salifert tests) and all of them agreed on where the the 5ml mark should be. So like you I disregard the screened line and just use a syringe.

The only nit I have is in your order of equipment "tank, stand, light, lid, filter, substrate". I would leave off the lid for a SW aquarium. It can be a cause of low pH.
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