

🧬 Keep your aquarium thriving—test smarter, not harder!
The API NITRATE 90-Test Kit offers a professional-grade solution for monitoring nitrate levels in both freshwater and saltwater aquariums. With 90 tests per kit, it delivers fast, accurate results within 5 minutes, helping prevent algae growth and invisible water problems that threaten fish health. Trusted by thousands of aquarists, this kit includes all essentials—reagents, test tube, and color cards—making weekly water quality checks effortless and reliable.













| Customer Reviews | 4.7 out of 5 stars 3,133 Reviews |
K**A
Good product, will buy again as needed.
This product works very accurately. Nice to be able to buy this separately and not purchase the whole kit. More expensive then the strips but I trust this process.
R**G
Great Test Kit for the price, it gives you a pretty good estimate of your Nitrates when they are high.
API kits are fairly accurate for the price, I highly recommend them for salt water aquarium owners that need and should have at least 2 kits of every important test type so they can cross reference results if they feel something is wrong with a particular test result. API fills that niche perfectly with pretty accurate easy to use kits that cost a quarter the price of the more accurate ones like Salifert, ELOS and Red Sea Pro. The API Nitrate Kit is as simple as it gets, just fill the vial to the marker or better yet use a syringe and add 5ml as directed. Then add 10 drops of reagent "A". swirl for a bit then shake reagent "B" for 30 seconds very vigorously and add 10 drops of that. Shake the whole thing for one minute vigorously and then wait 5 minutes to get a result. IMPORTANT NOTE: If you forget to shake reagent "B" you might as well throw the whole bottle of reagent out. This solution separates out in the container after a few hours into layers of different chemicals. If you don't shake it, you will be dripping out 10 drops of just one of those chemicals and remaining mixture will be compromised. The end result is that the next time you use it and shake it up properly the typically result is a lower reading than normal. Just remember to always shake reagent B properly for 30 seconds and you wont have any problems. If your Nitrates go down to reading Zero on the API kit, then it's time to move to a more accurate kit that is designed to read very low Nitrate levels. If your keeping a SPS Reef Tank you need the Nitrates to be near Zero and the API kit will not be accurate enough to read the small amounts that may be in your aquarium. For FOWLR Tanks, Nitrate is not as not as big of an issue, so an API kit or two is all you will probably need.
A**Y
Excellent economical test kit with limited capability
I worked in three pet shops as a teen and later managed the slat water department in a very large pet shop in Philadelphia. I have kept fish since I was five years old but have been on hiatus for the past 20 years and not had any tanks. These kits have been around for ages and are very accurate if you use them for their true intended purpose; freshwater community tanks or similar. Don't try and use these the nitrite or ammonia for saltwater tanks of any sort. Don't use the pH test kit for tanks that need exact pH values for high pH animals like cichlids (though this is less of a problem if you read below). These tests are extremely economical and provide many more tests per dollar than any other kits available. My son is six and my daughter is four. We decided to raise tadpoles twice this year and needed to monitor ammonia, nitrite, and pH. The 40-ish year old design of these kits still fit that bill perfectly and were exactly what we needed. I wish the scale on the pH kit went higher, but it goes high enough for community fish. Tadpoles here tend to like higher pH values of ~8.2 and the pH kit doesn't go that high. However, I got a rough enough estimate if the pH test indicated that the pH was off the chart high as water isn't going to go much above 8.2 unless you use chemical inappropriately. Ammonia and nitrite test kits worked perfectly as in the past and averted many potential tadpole disasters and crying children. We've kept snails, clams, some minnows, and loads of plants in the tank while the tadpoles have developed so the bio load was always changing. Still great kits even after 40 years at a very affordable price. Highly recommended for their intended usage scenario.
A**U
Great product.
Great product fast shipment
M**I
Ask yourself - Does it have Orange when looking at results.
This Nitrate test is very good. Honestly, I used both the Salifert and API versions and they both work good. What is nice about the API version is that you can use the acid to test if rocks have carbonate in them by dropping a couple of drops on a rock to see if it bubbles. (look it up). Also, about the colors. It gets hard to distinguish the colors. The way that I do it, is I ask myself "does it have orange in it? If so, then it is one of the Orange. Then I ask myself if there is no orange then it is red! Or if their is no orange then it is Yellow. Seriously! Try it!. Do the test. Ask yourself if it has orange, or STILL has orange. it will then be easier to match to the card! I hope I explained that well. Good Luck
I**H
Works great but please read.
Works good, but make sure you aren’t holding the tube directly against the card, otherwise you get weird light reflection and a skewed color. Hold the tube in direct, outside light ideally and about 1/2” to 1” away from the card until the color palette coordinates between the card and tube of water. As you can see in my picture, I’m holding it away from the card to get the correct color, if it gets held too close, the color matches nothing on the card.
M**.
Best test chemicals for ensuring quality water testing
Love the API test kits for my aquariums. Simple easy to use and easy to read results
D**.
Great replacement for Master Kit.
This test kit I got to refill my master test kit. The Nitrate test runs out first because of the number of drops required for each test.
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