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API SALTWATER MASTER TEST KIT 550-Test Saltwater Aquarium Water Test Kit

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Style: Saltwater


Features

  • Contains one (1) API SALTWATER MASTER TEST KIT 550-Test Saltwater Aquarium Water Test Kit, including 6 bottles of testing solution, 1 color card and 4 test tubes with cap
  • Helps prevent invisible water problems that can be harmful to fish and cause fish loss
  • Accurately monitors 4 most vital water parameters levels in saltwater aquariums: high range pH, ammonia, nitrite and nitrate
  • Designed for use in saltwater aquariums
  • Use for weekly monitoring and when water or fish problems appear

Description

Protect marine fish and invertebrates from unsafe water conditions with API SALTWATER MASTER TEST KIT. Fish waste, uneaten food, plant refuse and other organic compounds can create harmful levels of ammonia, nitrite and nitrate as well as cause drastic fluctuations in pH. These unhealthy conditions can result in fish stress, gill and tissue damage and even death. The API SALTWATER MASTER TEST KIT accurately measures these four saltwater parameters that are key to keeping your aquarium healthy. It includes six bottles of liquid test reagent, four test tubes with snap-tight caps, a holding tray and a step-by-step instruction booklet with information on how to correct unsafe water conditions. Simply fill a clean test tube with 5 ml of water, add the appropriate test drops and compare results with the color chart. Then follow the recommendations to modify conditions if action is needed. With API aquarium products, it’s easy to keep a beautiful saltwater, freshwater or reef aquarium. For almost 60 years API has developed premium solutions with proven and effective results for your family and ours. API offers a range of testing kits, water conditioners, and nutritionally superior food, because we’re dedicated to making a better underwater world. They work to provide a safe, hospitable environment for fish such as tropical community fish, cichlids, goldfish and more. At API, we understand the rewards and relaxation of fishkeeping because we have a passion for fish too.

Is Discontinued By Manufacturer ‏ : ‎ Yes


Product Dimensions ‏ : ‎ 7 x 5.75 x 4.75 inches; 1 Pounds


Manufacturer recommended age ‏ : ‎ 1 month and up


Item model number ‏ : ‎ 401M


Department ‏ : ‎ Unisex-Adult


Date First Available ‏ : ‎ June 20, 2004


Manufacturer ‏ : ‎ Mars Fishcare


Best Sellers Rank: #1,858 in Pet Supplies (See Top 100 in Pet Supplies) #2 in Aquarium Test Kits


#2 in Aquarium Test Kits:


Item Weight: 1 pounds


Department: Unisex-Adult


Manufacturer: Mars Fishcare


Item model number: 401M


Date First Available: June 20, 2004


Item Package Dimensions L x W x H: 6.69 x 5.16 x 4.4 inches


Item Dimensions LxWxH: 7 x 5.75 x 4.75 inches


Item Weight: 1 Pounds


Brand Name: API


Target Audience Keyword: fish


Directions: Follow the instructional booklet directions for individual testing of each water parameter, and test weekly for best results.


Country of Origin: United States


Model Name: SALTWATER MASTER TEST KIT


Color: No Color


Size: 1-Pack


Material: Plastic


Number of Items: 1


Style: Saltwater


Included Components: API Saltwater Master Test Kit


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Sunday, Dec 28

This item is non-returnable:

Non-returnable. Transportation of this item is subject to hazardous materials regulation

View our full returns policy here.

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Top Amazon Reviews

    • Better than strips!
Style: Freshwater
Accurate and reliable results. Much better than the strips
Reviewed in the United States on October 30, 2025 by Amazon Customer
    • Super helpful and Easy
Style: Freshwater
I got this freshwater test kit (the API one), and it’s been great. It comes with everything you need to check your tank water—like ammonia, nitrite, nitrate, and pH. The instructions were easy to follow, and the results are pretty easy to read once you get the hang of it. It does take a few minutes to do each test, but it’s not hard at all, and I feel a lot better knowing what’s going on in my tank. I’ve got a 35-gallon setup, and I use it about once a week to make sure everything’s on track. Way more accurate than the strips I was using before, and the kit lasts a long time. Definitely worth it if you care about keeping your fish happy and healthy. ... show more
Reviewed in the United States on July 23, 2025 by Jennifer Esquivel
    • accurate and easy to use, but buy with syringe/pipette
Style: Freshwater
easy to use and accurate. it's a bit expensive up front, but i'd say it's cheaper and more valuable in the long run because of the accuracy and amount of uses compared to disposable strips. the only comment/recommendation i have is to also buy a pipette or syringe with this to fill the 5 mL tubes for accuracy and convenience. i'd say this is a must have if you value your aquarium's well being ... show more
Reviewed in the United States on July 27, 2025 by mac
    • The best freshwater basic testing kit...
Style: Freshwater
You will find this freshwater kit is far more accurate than test strips. The soaking of a tiny doped pad method of test strips just isnt an accurate way to test. This is the industry standard water test kit that most aquarists swear by. 1st, be sure the test chemicals you get are not near expiration. You should easily be able to use this kit for up to a few years before the chemicals included lose their effectiveness. The expiration date is on the kit box and on each bottle of solution. The glass test tubes that used to be included in this kit have been replaced by plastic ones. The glass tubes made cleaning up a breeze and were far better than the plastic ones that don't clean up as well. Also the 5ml fill line is a bit difficult to see on the plastic tubes. It was always inevitable though that you would eventually break a few glass tubes before you got through the 800 tests this kit can provide. They now just assume that by the time the plastic tubes get permanently stained, you'll be on to a new test kit with new tubes. While not a deal breaker, I prefered the glass tubes. Be sure you purchase the kit best suited for the tanks or ponds you keep. This kit is the freshwater version. This kit tests pH in two different ways. If you have ph generally higher than 7.4 you use the high pH test solution. If you have pH below 7.6 youll use the standard pH test kit. This is great of you are keeping multiple tanks with different pH levels or if your one tank tends to bounce around between 7.4 to 7.6. Once you figure out which test best suits your aquariums, youll likely not use the other solution. This kit tests for total ammonia using 2 solutions in one test. Ammonia is a very hazardous chemical to your fish and plants. Use this kit to keep these levels of ammonia at or near 0. This kit tests Nitrites using 1 solution. This is the second step in the nitrogen cycle. While not as harmful as ammonia, it's still something you should strive to get as close to 0 as possible. Now some people using heavily planted and fertilized tanks will actually strive to have this level low but present. This kit tests for nitrates in two solutions for 1 test. While nitrates are not as harmful to fish as Ammonia or Nitrite, most fish keepers still strive for low readings. Long term exposures to high nitrates can still cause harm to fish. Generally youll get rid of nitrates by water changes or heavy plant growth. Many people with heavily planted and fertilized tanks prefer this value to be a little higher to feed the plants but still low to protect the fish. With this test kit testing 4 of your most important chemicals in fresh water, it is a necessity to have on hand. Test strips might be more convenient but are seldom very accurate. This liquid master test kit is the standard if you want true values at an affordable price. It comes in several varieties, depending on whether you have freshwater, marine, reef or ponds. Its a great way to see what is going on in your setup before any loss of life occurs. ... show more
Reviewed in the United States on June 7, 2024 by Don Gray
    • Perfect!
Style: Freshwater
It’s an absolute necessity for the aquarium hobby! It comes with everything you need to tell if you water is safe, except one thing, a gH test.
Reviewed in the United States on November 12, 2025 by Purchaser
    • Comprehensive and Easy-to-Use Freshwater Test Kit
Style: Freshwater
The API Freshwater Master Test Kit is an excellent tool for maintaining a healthy aquarium. This 800-test kit provides everything needed to monitor key water parameters, including pH, ammonia, nitrite, and nitrate, making it perfect for both beginners and experienced aquarists. The instructions are clear and easy to follow, and the color-coded results make reading the tests straightforward. The reagents and test tubes feel high-quality and durable, and the kit is well-organized for convenient storage. Overall, this is a reliable, comprehensive, and user-friendly test kit that helps keep freshwater tanks safe and thriving. ... show more
Reviewed in the United States on November 16, 2025 by tara speece
    • A fish lovers must!
Style: Freshwater
This test kit has been a game changer for my freshwater tank. It includes everything I need to monitor ammonia, nitrite, nitrate, and pH levels. The instructions are clear and the color chart is easy to read, even for beginners. It works well and will keep your fish safe for any size tank :) I test weekly, and this kit has helped me stay ahead of any water quality issues. It’s lasted a long time and the case keeps everything organized. If you’re serious about fishkeeping, this kit is an absolute must. Although it can get pricey, it’s extremely worth the value! ... show more
Reviewed in the United States on August 2, 2025 by H. Lincoln

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