API Phosphate PO4 Freshwater & Saltwater Aquarium Test Kit, 150 count

Rated 4.4444 out of 5 stars
$14.98Chewy Price
$20.98Chewy Price
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About This Item


  • Helps maintain a healthy aquarium by allowing you to measure and control phosphate levels.
  • Frequent testing is recommended to ensure your tank is healthy for your aquarium life.
  • Prevents potentially harmful algae and green water blooms in fresh water.
  • Promotes the growth of hard corals in salt water.
  • Kit includes two bottles of liquid test reagent, two-color cards, glass test tube and information on how to correct water condition.

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Play Video: Learn More About API From Our Team of Experts
Learn More About API From Our Team of Experts

Help keep your aquarium in tip-top shape with API's Phos-Zorb filtration pouch.

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Total Price: $27.82

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 TypeBetta, Bottom Feeder, Cichlid...Betta, Bottom Feeder, Cichlid...Marine Fish, Marine InvertebrateBetta, Bottom Feeder, Cichlid...Betta, Bottom Feeder, Cichlid...
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Questions & Answers

1 Customer Questions

Can this be used to test swimming pool water?
Answer by ChewyJul 04, 2021
This test kit is designed to measure phosphate levels in aquariums.

ReviewsWrite a Review

Rated 4.4444 out of 5 stars
9 Ratings
Would recommend to a friend

9 Customer Reviews

Rated 5 out of 5 stars
By Huffnpuff on Apr 26, 2022

Very easy to use

This test is very quick and accurate. Will definitely buy again.

Rated 5 out of 5 stars
By Goldfish on Dec 24, 2021

API test product

I received this product right away as it was needed to find out why I keep getting black beard algae in my aquarium.

Rated 5 out of 5 stars
By 1234 on Jan 22, 2021

Accurate phosphate aquarium testing.

I checked the tap water and the aquarium water. Both tests showed normal phosphate levels. Therefore, the algae bloom is probably not caused by excess phosphates in the water.

Rated 2 out of 5 stars
By Sheila on Mar 16, 2020

Very leaky test tube

I'm sure it tests for phosphates as advertised. I'm not a chemist or have other means to test for it, so I'll trust what the test says. However the cap for the testing tube is nowhere near leak proof. As part of the test process they want you to shake the vial vigorously 2 different times. I couldn't even tip it to the side holding it still without it leaking let alone shake vigorously without slinging chemically treated water all over. I tried it 4 times, once while testing, then three times with tap water. I would think they would have the vial be water tight, I mean that is the business they're in- water testing. Maybe my standards are too high. Maybe I got a bad cap. Whatever the reason, the world keeps turning.

Rated 4 out of 5 stars
By allieazalea on Jun 26, 2020

I have leaky tube too

Great for measuring phosphate levels for any kind of water

Rated 4 out of 5 stars
By Mango on Feb 10, 2019

Aquarium water chemistry tests

I have algae growing everywhere in my tank so I have started testing for all kinds of elements. I rated this product 4 stars instead of 5 stars because the test itself is a little difficult to read. I need to count the drops of reagent and judge color. It is not a black and white test. Otherwise the product is outstanding

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

Great test kit!

A necessity for testing my pond! Delighted that Chewy carries this!

Rated 5 out of 5 stars
By sherri on Sep 9, 2017

fish supplies

The product is great. Luckily we are into fish tanks because the glass tube came broke but no biggie.

Rated 5 out of 5 stars
By AEjr on Nov 18, 2016

Phosphate test kit

It is ez to use, comes with instructions on how to use and color chart that way you can see your phosphate leave.