Water testing is one of the most important parts of keeping a happy, healthy aquarium, but it can also be one of the most confusing.

So, we’re going to keep it simple.

I’m going to teach you how to read an aquarium test strip my way….. in plain English.

There’s no reason to buy a bunch of different expensive test kits or electronic meters to try to get an accurate of a reading as possible unless you are keeping a reef aquarium.  For a freshwater tank and a basic saltwater tank, everything you need to know can be read on a simple dip style test strip.  The test strips I use are by Tetra although there are others on the market.  Check yours to see what order the pads are arranged on the strip.

More Info Tetra EasyStrips 6-In-1

We will start with the pad labeled pH.  In a really rough, non scientific explanation, pH is how much acid is in or not in the water.  Why does this matter?  Fish originate from different pools of water all over the world that have different pH levels.  Some like high pH (low acid) and some like low pH (higher acid) and some like neutral pH (in between).  For instance, cichlids (sick-lids (not chic-lids)) from South America are from waters with a lower pH while cichlids from Africa are from waters with a higher pH.  Most freshwater fish can be tolerant of different levels, though.  In fact, a lot of the fish that you buy in stores are bred in Florida and are used to pH levels different from their native waters.  In a freshwater tank, I would go for a neutral pH of 7.0 unless you are keeping specialty fish or are trying to breed something specific.

A word of warning:  pH levels are logarithmic (sorry…big word) which means that 7.0 is 10X higher than 6.0, and 8.0 is 100X higher than 6.0  and so on.  Do not change the pH level very much at a time or it can stress the fish.  In fact, if the pH is in a range of 6.5 to 7.5 in a freshwater tank, I usually don’t try to change it unless I’m keeping specific fish like African cichlids or if the alkalinity is getting low.

What I normally use is a product called Seachem Neutral Regulator which puts the pH at 7.0 and keeps it there.  It works very well and does some other things to help keep the pH stable.  DO NOT use products that change the pH one way such as ones labeled pH UP or pH DOWN.  You run the risk of going too high or too low and stressing the fish out while doing it.

Saltwater fish should always be kept at a pH around 8.2 since that is the pH of ocean water and they are not very tolerant of other levels.  Seachem Marine Buffer does a nice job of keeping the pH there.

More Info Seachem Neutral Regulator

More Info Seachem Marine Buffer

The next pad is Alkalinity.  I’m all about knowing what the alkalinity level is!  Again, in basic terms, alkalinity is an indicator of how easily the pH can change.  If the alkalinity is low, pH can easily change…. which is bad.  If it is higher, pH will be more stable…. which is good.  A chemical called a “buffer” will help to boost alkalinity and make the pH more stable.  The two Seachem products mentioned above are good examples of that.  Alkalinity can go down naturally in an aquarium while the pH remains the same.  Once it gets too low, though, pH can change fast.  Keep tabs on the alkalinity level so you can keep in front of the pH level.  Use one of the buffers mentioned above if alkalinity starts to get low even though the pH is fine.

Then there’s chlorine.  If your water comes from a city water system, it may contain chlorine as a disinfectant.  This is easily removed with a chlorine remover available at most all pet stores.  There should never be a chlorine level in the aquarium while fish are in it.  You may also get a chlorine reading if you bleached decorations and put them back in without rinsing them out thoroughly.  Add chlorine remover if so.

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Next is Hardness.  This is how hard or how soft your water is and is only relevant in a freshwater aquarium.  The reason you want to know this is because it is tied to the pH of the aquarium.  Where I live in Arkansas, the water is naturally soft.  In some areas in the northern part of the state, the water is naturally hard.  I’m able to easily adjust the pH to where I want because it is soft and doesn’t have a lot of mineral content (hardness).  Mineral content acts like a natural buffer (similar to alkalinity) and can keep the pH from changing.  If your water is hard and the pH is high, you will have a difficult time lowering your pH.  Some fish don’t like a really high pH and they don’t do very well.  One of the pet stores in north Arkansas that I consult with had to stop carrying certain fish and stop doing large water changes because they couldn’t lower the pH.  If you happen to have hard water and a naturally high pH, there are products that can help to soften the water and lower the pH but that can get expensive to do on a long term basis.  I would just choose fish that like hard water such as African cichlids.  If your water is soft, use one of the Seachem products above and you will be fine.

The next pad is nitrite.  Nitrite is the second stage in getting rid of fish waste (ammonia) in an aquarium though biological filtration.  Ideally, nitrite should always be “0” in the aquarium.  The only time you should have a nitrite reading is when the aquarium is new and is cycling.  If you have nitrite and your aquarium is over 6 weeks old, you are either feeding too much, have too many or too large of fish for the tank, or over cleaned the aquarium and killed the good bacteria.  As long as it is in the safe range in a new tank, you should be fine.  If it is over the safe range, do a large water change, add bottled bacteria such as Seachem Stability to boost the cycling process and cut feeding by half or more until the reading is “0”.

More Info Seachem Stability Fish Tank Stabilizer

 Last is Nitrate.  This pad is the “dirt-o-meter” of the aquarium.  The higher the nitrate reading is, the dirtier your aquarium water is…. even if the water looks clear.  It is the dissolved organic junk that’s in the water.  Nitrate is the last product of biological filtration and is removed most effectively with water changes.  Nitrate is read in ppm such as 10 ppm, 40 ppm, etc.  An easy way to know how much water that needs to be changed in the aquarium is by the reading number.  If it is 10 ppm, change 10% of the water.  If it is 40% which is at the end of the safe range, change 40% of the water.  If it is getting really high such as 80 ppm, then you need to change about 50% of the water, wait a week, then change another 50%.  Keep doing this until you get the nitrate to a safe level.  If you can keep it in between the 20 ppm – 40 ppm range and do regular water changes, you will be fine.

That’s it! That is my simple, highly non-scientific way to judge the health of an aquarium with a multi-test strip.

I hope this article helped you in some way!  I like taking topics like this that can be confusing and teaching them in a way that is easier to understand. 

I was wondering, though, if you could take a minute and help me out in return?

I’m in the process of taking these articles off of my local maintenance business website (where you’re at now) and creating a new website dedicated to articles that will help you guys from my 25 years of aquarium maintenance business experience.

I want to find out what you guys are struggling with the most so I can create articles that will help you the best.  This new website should be ready in early 2021.

I would really appreciate it if you would take this short survey so I can collect these problems and also some demographic info so I know how best to write.  You can access the survey here:


If you would like to be notified when the new site goes live, you can sign up below.

If you do, I will send you the article Top 4 Aquarium Algae Cleaning Tools I use in My Business.

Thank you for your help!  I hope you have a blessed day.




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Larry has been in the aquarium industry for 20+ years doing everything from retail, maintenance, publishing, commercial repair and consulting. He lives with his family on their 10 acre "farm" .... which is just a code word for "petting zoo". His "happy place" is sitting on his John Deere tractor.