Replace old test kits

Replace your old test kits

Welcome to Day 29 of the 31 Days to Build a Better Saltwater Aquarium Challenge.

Today’s task is to replace your old test kits.

How old are your test kits, anyway?

How long have you had your old test kits? Are they still good, or have they expired?

If your test kit has expired, it may not be providing you with reliable results. Just because the test kit has expired doesn’t mean that it absolutely will give you unreliable results, it just means that the manufacturer has proven that it will provide reliable results. Intuitively, this makes sense.

Most of the kits we use involve careful titration of solutions and visualization by color changes. If the concentration of the solutions drifts over time, or if the stability of the solution changes over time, your results may become skewed.

For today’s build a better aquarium challenge, I want you to take a look at your test kits and find the expiration dates. If they are expired, please replace them. I know these kits can be expensive, and I know that it feels crummy throwing away a kit that is half-full, but there is no sense in keeping the kit around, if you it won’t give you good results. In fact, it is actually more dangerous than not testing at all.

Replace old test kits

For example, let’s consider three scenarios.

Scenario 1: You don’t use a kit at all

In Scenario 1, let’s assume you don’t use a test kit at all. You either threw away the old test kit and never replaced it or never had one, in the first place. Now, let’s assume you notice a small problem with your tank. Well, where do you start? What’s the problem? You’re not going to know–but I think you would agree that it seems like an easy conclusion to think that there probably is a water quality problem of some sort. In this case, you would likely take action.

Scenario 2: You use an old test kit that (unknown to you) gives a false high result

In this scenario, the old test kit, that you did not replace, gives you a false high result. To take a real example here, perhaps it is your pH test, and it reads off the charts high. Well, in that case, you may start to take measures to lower the pH, and you could be chasing down a number that is otherwise perfectly fine. Not good. If the kit is your nitrates test kit, it is possible that all it does is make you work much harder, focusing on removing nitrates from the water that just aren’t there–they just look like they are there, because your kit is wonky.

Scenario 3: You use an old test kit that (unknown to you) gives a false low result

In Scenario 3, let’s assume the kit gives a low result, meaning it masks the problem. You notice something is off in your tank, you use your test and everything looks normal. Are you going to take the problem seriously? Probably not. In fact, you may feel so certain that the water quality is fine for whatever test we are discussing and may ignore the solution that would otherwise be obvious to you.

Let’s also start a collegial competition to see who is throwing out the oldest (I guess farthest past the expiration date) test kit.

Here’s what mine say:


Mine expired March 2017. Time to buy some new test kits.

It ought to be pretty easy to beat my expiration date. Post your dates below (if you dare!)







One response to “Replace your old test kits”

  1. Yvonne Galloway

    I replaced my Mg test and found out my stats were ok. That is, if the new one is accurate.

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