The short answer
API’s liquid master kit reads ammonia; the multi-strips from API, Tetra and Aquarium Co-Op leave ammonia to a separate test but add GH and KH. Across 14 soft-water tanks, a Glass Box Diaries writer found strips close to liquid for nitrite, nitrate, pH and KH, with the API ammonia strips and one brand’s GH pad the exceptions.
The kits here are for freshwater; strips and Seachem’s kit are also sold for salt water. For reef tanks, start from our Saltwater & Reef section.
Liquid Kits and Test Strips Side by Side
Figures are the makers’ own; ppm equals mg/L (API). API master-kit figures are from its directions as reproduced by UF/IFAS Extension.
| Attribute | Liquid kits | Test strips |
|---|---|---|
| Ammonia | Total ammonia, 0 to 8.0 ppm (API master kit) | Not on API, Tetra or Aquarium Co-Op multi-strips; API ammonia strips read 0 to 6 ppm |
| GH and KH | Not in API’s master kit | On all three multi-strips |
| Nitrite range | 0 to 5.0 ppm (API master kit) | 0 to 10 ppm (API 5-in-1) |
| Nitrate range | 0 to 160 ppm (API master kit) | 0 to 200 ppm (API 5-in-1) |
| pH range | 6.0 to 7.6, or 7.4 to 8.8 with the high-range test (API) | 6.0 to 9.0 (API 5-in-1) |
| Chart steps (as published online) | Seachem MultiTest (drops and powder): “Detectable changes on the color chart in 0.1–1 mg/L increments”; API’s liquid steps are on the kit’s printed color card | Nitrite 0, 0.5, 1, 3, 5, 10 ppm; nitrate 0, 20, 40, 80, 160, 200 ppm (API and Tetra) |
| Read time | 5 minutes for API’s ammonia, nitrite and nitrate | Up to 60 seconds (API, Tetra, Aquarium Co-Op) |
| Tests per kit | 800 in API’s master kit (listing title); over 75 in Seachem’s MultiTest | One strip per test, all pads at once; 25 to 200 per Aquarium Co-Op bottle |
| Storage | Cool, dark place (Seachem) | Cap closed, strips dry (API, Tetra, Aquarium Co-Op) |
The ammonia row matters for a new tank: API advises testing ammonia “several times a week for 4-6 weeks when you start a new aquarium”. See what causes ammonia in a fish tank.
Are Aquarium Test Strips Accurate?
API says its ammonia strips are “extremely accurate in showing high ammonia levels”, a claim limited to high readings. Aquarium Co-Op, an aquarium retailer that sells its own strips, built them “to be fast, comprehensive, and accurate”. Tetra’s page says its 6-in-1 strips beat other products on accuracy. None of the three publishes an accuracy tolerance on the pages read.
The closest thing to a side-by-side check is Glass Box Diaries, an aquarium website that calls itself independent and earns affiliate commissions. Its writer, Shaun, compared the API Freshwater Master and API GH & KH liquid kits with API 5-in-1, Easytest 6-in-1 (not Tetra’s EasyStrips) and API ammonia strips across 14 of the writer’s own aquariums, every kit “purchased the day before testing began”, comparing the readings with each other:
- Nitrite, nitrate, pH and KH: the writer’s accuracy table rates them “Either Method Works”.
- Ammonia: the writer found the API ammonia strips “far more difficult to read” than the liquid test.
- GH: the API 5-in-1 stayed close to the liquid tests, while “the Easytest 6-in-1 Test Strips regularly reported far lower GH values.”
The overall verdict, which also weighs ease, speed and cost per test: “While liquid test kits came out ahead overall, the results weren’t as one-sided as I expected.” The tanks had soft water, nitrate of 0 to about 15 ppm, pH of about 6.4 to 7.6 and KH of 0 to 5 dKH; the findings cover that range.
Owners report failures on both sides:
- Strips, ammonia: on MonsterFishKeepers in July 2024, a keeper’s Tetra ammonia strips read 6 ppm in three tanks described as “cycled and very mature”; the poster wondered whether “a very humid basement” was why.
- Strips, pH: on r/Aquariums in 2023, one owner’s Aquarium Co-Op strips gave “a 6.4-ish pH reading even though API pH test gives a reading of 7.2+”. After about a year, the owner wrote, they gave “a more accurate reading of pH”.
- Liquid, technique: on Fishlore in 2018, the thread starter wrote: “I’ve had many liquid tests I’ve had to redo because of one extra drop.”
- Liquid, time and colors: in the same 2023 thread, a commenter who works in a store that sells Tetra strips said the API kit can take “at least 10 minutes” without the drop counts and wait times memorized, and “With the api vials it is difficult to see the difference between the colors”.
What Throws Each Format Off
Strips
- Moisture. API: “Keep wet fingers out of tube. Close tube tightly after removing strip. Store in a cool, dry place.” Aquarium Co-Op: “The test strips must stay dry for optimal accuracy.”
- Age. Aquarium Co-Op: “Test strips expire 2 years after production.”
Liquid kits
- Shaking. API’s nitrate directions (UF/IFAS copy): “Vigorously shake the Nitrate Test Solution #2 for at least 30 seconds. This step is extremely important to insure accuracy of test results.” The capped tube is then shaken for 1 minute.
- Light, heat and age. Seachem: “Analytical reagents, dry or liquid, tend to be adversely altered by light and heat. It is a good idea to store kits in a cool, dark place.” In a 2021 r/Aquariums post, an owner’s API kit that had expired in 2016 matched a new kit on every test except nitrate, in a week-old tank; the owner’s answer on accuracy was “sort of”.
- Ammonia binders. API’s ammonia directions, as reproduced by UF/IFAS Extension, say the kit “will still test positive for ammonia, even though treating with AMMO LOCK has made it non-toxic.”
pH in soft water carries a caution for both. Tetra says KH should be at least 120 ppm for an accurate pH reading on its strips; Seachem says of pH kits in general: “Weakly buffered water will give unreliable results”.
Safety
The data sheet API’s master-kit page links as “Freshwater MTK SDS” carries, for its nitrite test solution, the signal word “Danger” and says: “Causes severe skin burns and eye damage.” “Suspected of damaging fertility or the unborn child.” “Keep out of reach of children.” “Wear protective gloves, protective clothing, eye protection and face protection.” “IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.” “IF exposed or concerned: Get medical advice/ attention.” Seachem’s kit insert says: “Components of this kit contain acids and organic solvents and may be hazardous if used carelessly.”
Which Aquarium Test Kit Is the Most Accurate?
No independent lab ranking of hobby kits turned up in our research, so the answer rests on what makers publish:
- Seachem MultiTest Nitrite & Nitrate states “Detectable changes on the color chart in 0.1–1 mg/L increments” and “contains a reference sample for validation”: a 10 mg/L nitrate solution tested in place of tank water to check the reagents.
- Hanna’s HI700 Checker, a digital colorimeter “For use with freshwater only”, lists accuracy of “±0.05 ppm ±5% of reading” at 77°F (25°C), over 0.00 to 3.00 ppm. Hanna reports ammonia as nitrogen (NH3-N). API’s pages say its kit reads total ammonia but do not name the basis, so check the units before comparing a Hanna number with an API one.
- API lists step values for its strips online but not for its liquid kits, whose steps are on the printed color card; it gives no accuracy tolerance on the pages read here.
Choose a Liquid Kit or Strips
Choose a liquid kit if:
- you are cycling a new tank and want ammonia, nitrite and nitrate in one kit, as API’s master kit has;
- you want to check the kit itself, as Seachem’s reference sample allows;
- you test only now and then: Glass Box Diaries’ writer notes that liquid reagents “may be less susceptible to repeated exposure each time you perform a test”.
Choose strips if:
- you want GH, KH, pH, nitrite and nitrate from one dip in about a minute;
- you run routine checks on an established tank, where Glass Box Diaries found API and Easytest strips, not Tetra’s, comparable for nitrite, nitrate, pH and KH (soft water, fresh strips).
Note
If fish look unwell, test the water at once with whichever kit you have, then contact an aquatic veterinarian. Our guide to why fish die in an aquarium covers the water causes to check.
| # | Preview | Product | Price | Link |
|---|---|---|---|---|
| 1 |  | API Freshwater Master Test Kit 800-Test Freshwater Aquarium…Liquid kit | $35.98 Prime | Check on Amazon |
| 2 |  | API 5-IN-1 TEST STRIPS Freshwater and Saltwater Aquarium…Dip strips | $24.98 Prime | Check on Amazon |
| 3 |  | Seachem MultiTest: Nitrite & Nitrate 75 TestsDrop-and-powder kit, reference sample | $22.14 Prime | Check on Amazon |
These three picks are compared with their verified specs in our best aquarium test kits roundup.
Ready to buy?
Our Water Care & Testing section gathers test kits, conditioners and bacteria starters.
Frequently Asked Questions
Q. Are test strips accurate enough for a betta or goldfish tank?
No maker publishes an accuracy tolerance for strips on the pages read. API’s 5-in-1 chart reads the same pads for both but, for pH, GH and KH, shades its ideal, caution and danger zones differently in the betta and goldfish rows, with different recommendations, and adds: “We also recommend testing for ammonia using the API Ammonia Test Strips or Kit.”
Q. What should aquarium test strips read?
API’s 5-in-1 chart says “In established aquariums the nitrite level should always be 0 ppm (mg/L)” and “A nitrate level of 40 ppm (mg/L) or less is recommended for freshwater aquariums.” Seachem says it is advantageous to keep nitrate “under 20 mg/L”; the makers’ figures differ. See our guides to high nitrite and high nitrate.
Q. How often should you test aquarium water?
API says to use its master kit weekly, and to test nitrite every other day in a new tank, then weekly once the biological filter is established, in about 4 to 6 weeks.
Q. Can you use these kits in a saltwater tank?
API’s master kit is for freshwater. API’s 5-in-1 strips are for fresh and salt water, but its chart says “The GH of salt water is above the range of this test”, and Tetra says its hardness pad is not used for saltwater readings.
Sources (19)
- API, Freshwater Master Test Kit (maker)
- API, 5-in-1 Test Strips (maker)
- API, 5-in-1 Diagnostic Chart (PDF) (maker)
- API, Ammonia Test Kit (maker)
- API, Ammonia Test Strips (maker)
- API, nitrite solution safety data sheet (maker)
- UF/IFAS Extension, Freshwater Water Quality Testing (PDF) (university extension)
- Seachem, MultiTest Nitrite/Nitrate (maker)
- Seachem, MultiTest instructions (PDF) (maker)
- Seachem, Guidelines for Using Test Kits (PDF) (maker)
- Tetra, EasyStrips 6-in-1 (maker)
- Tetra, EasyStrips 6-in-1 color chart (PDF) (maker)
- Aquarium Co-Op, Multi-Test Strips (retailer and strip maker)
- Hanna Instruments, HI700 Low Range Ammonia Checker (maker)
- Glass Box Diaries, Liquid Test Kits vs Test Strips (aquarium website, affiliate links)
- Fishlore, Why Is Everyone So Against Test Strips? (forum, 2018)
- r/Aquariums, Are test strips really so bad? (forum, 2023)
- r/Aquariums, expired vs new API test kits (forum, 2021)
- MonsterFishKeepers, Test strip’s accuracy (forum, 2024)
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
