API Stress Zyme Freshwater & Saltwater Aquarium Water Cleaner, 16-oz bottle - Chewy.com

API Stress Zyme Freshwater & Saltwater Aquarium Water Cleaner

Rated 4.8846 out of 5 stars

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About This Item


  • Keeps aquarium clean by reducing aquarium maintenance.
  • Contains over 300 million live bacteria per teaspoonful to consume sludge and organic debris, keeping gravel and glass clean naturally.
  • Use it weekly in fresh and saltwater aquariums to maintain a strong biological filter and a healthy, clean aquarium.
  • All natural formula adds beneficial bacteria for a healthier aquarium.
  • Helps boost the natural aquarium cycle.

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

Special Note
  • 8-oz bottle treats up to 470 gallons.
  • 16-oz bottle treats up to 940 gallons.
  • 64-oz bottle treats up to 3786 gallons.
  • 1-gal treats up to 7600 gallons.

About API Water Conditioners

It’s Smart To Be Proactive!

The best way to keep your aquarium clean is to maintain good water quality. This will help keep your fish strong and vibrant and prevent disease. Water conditioners and test kits from API can help you keep your aquarium water safe and healthy.

How Do I Maintain a Healthy Environment?

It is important to test your aquarium water weekly to ensure it stays healthy for your fish.  In addition, a bi-weekly partial water change of no more than 25% will help reduce toxic buildup, remove debris the filter missed, and replenish the oxygen available to your fish.

Feed Twice Daily and Test Water Weekly

Feed your fish twice a day, check their water temperature, and observe them to make sure they are active. You should also test water quality weekly for optimal safety. For fish to thrive, their water must closely match that of their natural environment—poor water quality can cause stress, illness and even fish loss. The 6 important parameters for healthy aquarium water are ammonia, nitrite, nitrate, pH and water hardness (GH & KH). All of these can vary over time and are invisible to the eye.

Change Water and Restore the Ecosystem

In a closed aquarium environment, there are no natural rivers or streams to carry away debris and other waste materials. That is why you should replace 25% of your aquarium water every two weeks, making sure to add water conditioner to your tap water to make it safe for your fish. You should also change your filter media and clean your gravel monthly. Adding beneficial nitrifying bacteria with API Quick Start when you do will help restore your aquarium’s fragile ecosystem and avoid disruption.

What Do API Products Do and When Do I Use Them?

API Test Kits

Use test kits weekly to monitor water quality parameters, which can vary over time and impact the health of your fish.

API Stress Zyme

Using this every week will help keep your aquarium clean and your gravel and ornaments sludge-free.

API Algaefix

Use weekly to control algae growth and keep aquarium glass, ornaments and plants clean.

API Stress Coat

Use every 2 weeks during water changes to make tap water safe, and when adding fish, or when fish are injured.

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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Questions & Answers

17 Customer Questions

Can I use Quick start & Stress zyme at the same time
Answer by ChewyApr 08, 2018
API products can be combined together to help clean and calm the fish.

What's the difference between stress coat and stress zyme? Do I need stress zyme if I have stree coat?
Answer by ChewyJan 12, 2021
Stress Coat is a dechlorinator product (will treat chlorine, chloramines, and heavy metals) with additional stress reduction properties to make sure that fish remain happy and healthy during water exchanges or other stressful times. Stress Zyme is a bacterial additive that should be added into the aquarium once weekly in order to reduce the amount of sludge, organics, and solid waste. This reduces overall cleaning maintenance and also ensures that you filter does not become clogged with waste between maintenance. Ideally, both of these products would be used.

Do you put this in while the fish is in the tank? Or take them or and do it and then return after specific amount of time?
Answer by ChewyMar 30, 2018
This water conditioner can be added while the fish are in the tank.

Do any of your larger bottle sizes (64oz/1gal) include a pump?
Answer by ChewyOct 24, 2017
These bottles don't included a pump.

ReviewsWrite a Review

Rated 4.8846 out of 5 stars
52 Ratings
Would recommend to a friend

52 Customer Reviews

Rated 5 out of 5 stars
By Jay on May 7, 2023

Happy zymes for happy fish

This product has been a fantastic addition to my tank maintenance routine. Water has been clear for weeks

Rated 5 out of 5 stars
By 3DoggyDad on Jan 27, 2023

Works Great

This really helps out in our 20g tank, water quality definitely improved the first time we tried it and have been using it for years.

Rated 5 out of 5 stars
By Kkkk on Dec 20, 2022

Stress zyme for aquarium water

Stress zyme is great because it contains good bacteria to use with each water change. This stuff really helps keep my aquarium so clean its amazing

Rated 5 out of 5 stars
By Lilly on Nov 16, 2022

Review of stress zyme.

I love stress zyme. I feel my fish do so much better with the extra touch of good bacteria.

Rated 5 out of 5 stars
By Gloria on May 20, 2022

Good Stuff !

I use API Stress Zyme to start new tanks and every time I do water changes. It really does prevent serious nitrate and ammonia problems in new tanks when used as directed.

Rated 5 out of 5 stars
By PetPerson on Jun 24, 2022

Great Product

This product is amazing for clearing water in my freshwater tank. Wish I had found it sooner.

Rated 5 out of 5 stars
By rhianna on May 21, 2022

best price ever

smaller sizes in stores cost more! wonderful product aswell, really helps with the gunk under the sand

Rated 5 out of 5 stars
By MemyselfandI on Feb 20, 2022

Great Product for Aquariums

This Stress Zyme was delivered quickly to my front door. I was so glad because i ran out unexpectedly. Thankyou Chewy!

Rated 5 out of 5 stars
By JimC on Jul 28, 2021

Great Product!

I use API Stress Zyme Freshwater in all of my 4 tanks after water changes! It helps maintain the good bacteria levels so the water remains clear. I highly recommend this product.

Rated 5 out of 5 stars
By Maintenance on Sep 6, 2021

Stress Zyme

Great product.! I use it for starting a new aquarium. Chewy delivered quickly.