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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: #1,362 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: Monday, Mar 2

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

    • Good product
Style: Freshwater
The kit works really well. My only complaint is that you only get 4 test tubes for five tests. I mean, sure, if your low ph is fine you don't need to do the high ph test, but mine is always borderline (highest on the low, lowest on the high), so I always need to do both. Otherwise, no complaints, and I figure that when the time comes that I DO need to order more, then I'll extra test tube. ... show more
Reviewed in the United States on December 2, 2025 by Cindy G.
    • Must have for aquarium enthusiast
Style: Freshwater
This test kit has most everything you need for testing your aquarium water. Good price compared to local prices. Easy to use and to read.
Reviewed in the United States on December 9, 2025 by Marilyn Slaughter
    • 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
    • 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
    • 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
    • A Must Have Test Kit For Every Level Of Hobbyist
Style: Freshwater
API is a giant among companies that provide aquarium related products.They have maintained their sound reputation by offering innovative products and resisting the temptation to tamper with those which are already established and are time proven, dependable performers.The Fresh Water Master Test Kit belongs in the arsenal of tank maintenance and care products for every level of hobbyist from beginner to advanced. It's important to understand that these kits provide an indication only - it's unrealistic to expect a pin point reading as the tests aren't intended nor made to deliver that. But rather, to enable you to get a decent reading of say, where your PH level is knowing the accuracy may be off a few points sure beats shelling out $200 for a good digital PH meter.It's critical to understand these limitations and that they apply to everyone of the four included tests. PH High Range PH Ammonia Nitrites Nitrates For must of us, Ammonia is the most important because it's the number one killer of aquarium kept fish. The others are important of course, but Ammonia levels should always be checked and checked often. It's also important to pay attention to the expiration dates of the liquid reagents. Expired reagents mean off the charts inaccurate readings. Along with the liquid reagents the kit includes, instructions both in a small manual and attached to each bottle of testing liquid, four test tube, four plastic caps and a color chart. To ensure you get the most accurate reading possible compare the finished result to the card color block in the best possible light and against the most pure white background you can find. Just like computer monitors many of us see color differently which is the inherent draw back of this type of testing. But again, there is nothing else on the market at this kind of price point which can give you enough information to correct and adjust your key water parameters. If you're just starting out in this wonderful hobby, you'll master using this kit in no time and it will help you maintain a healthy and flourishing aquarium. Remember to never, ever rinse even cleaned test tubes in your tank water - even very small traces of testing reagents can be lethal to your fish. Draw water from your tank using a large plastic syringe available at any drug store, super market, or add one to cart from Amazon. For a full range of tests that cover the four most significant parameters you need to stay on top of - you can't beat the API Master test kits, not at this price. You can also buy replacement API test tubes which are sold in boxes of a dozen or 24 at a reasonable price, and a steal at Amazon. ... show more
Reviewed in the United States on April 1, 2012 by Peter Suslock

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