API Replacement Test Tubes for Aquarium Liquid Test Kits, 24 count

Rated 4.5 out of 5 stars
$29.98Chewy Price
$41.98Chewy Price
$28.48Autoship Price
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About This Item


  • Every purchase comes with 24 test tubes and caps to replace lost or damaged tubes.
  • suitable for use with all aquarium water testing kits.
  • Clean, undamaged test tubes are an essential tool for keeping aquarium conditions healthy.
  • Dirty test tubes can alter water test results, making them less accurate.
  • Test tubes with cracks or other damage can leak or harbor bacteria which can also lead to inaccurate test results

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Check out API's master test kits to help keep your freshwater, saltwater or reef aquarium in tip-top condition.

About API Testing

Testing the Waters

For fish to thrive, their aquarium water must be similar to the water in their natural environment. Poor water quality can cause stress, illness and even the loss of your fish. Important water quality parameters include ammonia, nitrite, nitrate, and pH. These can vary over time, and they are invisible to the eye, which is why it is necessary to test weekly. Choose from a wide range of API testing options like the Freshwater Master Test Kit or 5-in-1 Test Strips to accurately evaluate your water.

Pressed for Time? Just Dip and Read

Simply dip an API test strip into your aquarium, swirl it twice, and then use the color-coded chart to determine if your water is within safe parameters or if adjustments are needed. That’s it! API test strips are available in a 5-in-1 version, which includes testing for pH, nitrite, nitrate, carbonate, and general hardness. Ammonia and pH test strips are also available so you can mix and match according to your needs.

The Scientific Approach

Get professional results from the comfort of your home with API test kits. Measure up to six parameters with API Master Test Kits, or pick and choose from a wide variety of individual test kits. Both types of kits come with test tubes and a laminated, calibrated color card. API test kits allow for numerous tests, making them an inexpensive way to help keep your aquarium water quality in check.

How to Correct Aquarium Water Parameters

Too Much Ammonia?

Ammonia is released into the water through gills, urine, uneaten food and more. API Ammo-Lock detoxifies it instantly.

Inappropriate pH Levels?

Fish require a specific pH level to thrive. Use API pH Down to lower freshwater aquarium water pH to the right level.

Too Much Nitrite?

Use API Quick Start to quickly consume nitrite and help maintain an active biological filter.

Nitrates Too High?

API Nitra-Zorb helps remove nitrate and other toxins that can be harmful to fish and lead to algae growth.

About API

The team at API has a passion for fish and understands the rewards and relaxation fishkeeping can bring. For almost 60 years, they have developed premium products with a focus on proven and effective results. API offers a range of testing kits, water conditioners and nutritionally superior fish foods. They are dedicated to making a better underwater world for the benefit of fish and those who keep them.

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Fish TypeBottom Feeder, Discus, Goldfish...Marine Fish, Marine InvertebrateMarine Fish, Marine InvertebrateGoldfish, Marine Invertebrate, Tropical FreshwaterGoldfish, Marine Invertebrate, Tropical Freshwater
Aquarium TypeSaltwater, Freshwater, PondSaltwaterSaltwaterFreshwaterFreshwater

Questions & Answers

2 Customer Questions

What is the proper way to clean these test tubes after each use?
Answer by ChewyJun 24, 2018
The tubes can be cleaned with hot water and air dried.

What size (dimensions) and capacity are these test tubes?
Answer by ChewyAug 10, 2021
The test tubes are meant to hold the water testing sample of about 5 milliliters (some rounding occurs here) marked with an indicator line and will hold 2-3 more milliliters if they are filled to the very top. The test tube is 12-13 millimeters in diameter and 85 millimeters in height. Using test tubes of different specifications with API reagents is not advised, for accuracy purposes.

ReviewsWrite a Review

Rated 4.5 out of 5 stars
8 Ratings
Would recommend to a friend

8 Customer Reviews

Rated 3 out of 5 stars
By Steve on Jun 9, 2021

Fragile Product...Sub-par Packaging

The extra supply of test tubes is much appreciated. However, the box the tubes were in had no cushioning whatsoever, nor did the shipping box. The tube box had opened and the tubes were scattered in the shipping box. Surprisingly only one tube was broken. The shipping box also contained an LED clip on aquarium light. I still recommend the products, but was disappointed in the lack of cushioning, both from API and Chewy. I still would order again, though. Just hope for better packing.

Rated 5 out of 5 stars
By Stacy on Sep 30, 2020

Great service

I trust Chewys for all my pet needs. It only takes a day or 2 for my orders to ship. I don't get charged till the items are on the way. I like that I can order prescriptions, and I love the way they keep me informed about the products and services. Buying at their phone app is so easy to navigate thru.

Rated 5 out of 5 stars
By Jenny on Nov 23, 2019

Test tubes for life

All intact! More test tubes than I even thought I needed.

Rated 5 out of 5 stars
By Delilah on Oct 14, 2018

When you have cats...

Replacements are necessary. My furry little friends love to knock over my test tubes...I now have a test tube rack because I was afraid they’d go to jump off the counter and come in contact with the broken glass! These are literally the same test tubes you get in the API test kits so I’m very happy to have them.

Rated 3 out of 5 stars
By BassetMom3 on Jul 13, 2018
Top 250 Contributor

Nice to be able to replace broken tubes

The second time I used my API kit I broke a tube. I got these and it has helped to have extra tubes on hand. I can also test all my tanks and then clean all the tubes instead of between each tank. It would just be nice if it wasn't so easy to break the tubes.

Rated 5 out of 5 stars
By ballen13 on Jun 4, 2018
Top 1000 Contibutor

Great Replacements

Accidents happen and it's always great to have these extra testing tubes on hand. Besides using them for Test Kits, I use them to store my Frozen Foods for the Marine Tanks and Freshwater Tanks, makes using the pipettes so much easier for proper doses.

Rated 5 out of 5 stars
By KittyLover on Sep 22, 2017
Top 100 Contributor

Delighted they have replacements tubes!

So glad I did not have to buy new test kits just to replace old tubes! This is a winner!

Rated 5 out of 5 stars
By Pepper on Sep 18, 2017

On line order

My order came quickly, and since they were glass tubes..unbroken!