Aquarium water test log apps for iPhone: 8 compared

If you want an iPhone app to log your aquarium water tests, the right one depends on what else you want from it. For a plain, free log of every tank: Aquarium - Log Tracker, which I built, so weigh that. For a reef with a controller: AquaticLog. For a species library with compatibility checks: Aquarimate or Pocket Marine. To read test strips with the camera: AquaLens. To know where a new tank is in its cycle: Nitrify. Each section below says where an app is the better pick, mine included.

The short version:

Free, every tank, no account: Aquarium - Log Tracker.
Reef with an Apex, Hydros or Seneye: AquaticLog.
Species library and compatibility, pay once: Aquarimate ($9.99) or, for marine, Pocket Marine ($3.99).
Scan test strips, identify fish from a photo: AquaLens.
Cycling a new freshwater tank: Nitrify.
Fish plus reptiles or other pets: Fishi.
Reef with an AI assistant: Reef Buddy.

How the eight apps compare

App	Tanks	Camera reads tests	Species library	Account needed	Price (US)
Aquarium - Log Tracker	Fresh and salt, unlimited	No	No	No (optional sync)	Free, no in-app purchases
AquaticLog	Fresh and reef, several	No; reads controllers	Livestock records	Yes	Free download
Aquarimate	Fresh and salt, unlimited	No	Yes, with compatibility	No (optional cloud)	$9.99 once
Pocket Marine	Saltwater	No	800+ marine species	No	$3.99 once
Fishi	Fish and other pets	No	Hundreds of species	Not stated	Free download; subscription
Nitrify	Freshwater; 1 tank free	No	No	No (iCloud)	Free; Pro is a one-time unlock
AquaLens	Fresh and salt	Yes, strips and liquid kits	Photo ID	Not stated	Free to start; Pro
Reef Buddy	Reef	No	No	Syncs across devices	Free; premium AI

Everything here is from each app's App Store listing in November 2026. "Not stated" means the listing doesn't say.

What makes a water test log worth keeping

A single test says where the tank is today. A log says which way it's going: nitrate climbing between water changes, alkalinity swinging, a heater that sticks. Three details decide whether an app's log is trustworthy.

A blank stays blank. "I didn't test nitrite" and "nitrite was zero" are different facts. An app that stores the first as the second draws trends that never happened.
Units follow your kit. Nitrate as NO3 or NO3-N, alkalinity as dKH, meq/L or ppm. Mixing them makes a chart lie by a factor of four or more.
Free ammonia, not just total. Most kits read total ammonia, but the toxic part is un-ionised ammonia (NH3), and its share grows with pH and temperature: roughly ten times larger at pH 8 than at pH 7.

Then there's what you want beyond the log: reminders, a species library, camera scanning, controller data, or help while a new tank cycles.

Aquarium - Log Tracker: a free log for every tank

Aquarium - Log Tracker puts every parameter a tank tracks on one page, with your last values in grey, and a timer per test for the wait between reagent and reading. A field you leave blank is never stored as zero. After you save, it works out free ammonia from the pH and temperature in the same session and flags readings outside the tank's target band.

All parameters share one time axis on the charts, so a temperature spike and a nitrate spike line up, and livestock losses are marked across all of them. There are reminders for water changes, testing, filters and dosing across every tank, a livestock and equipment list, and a journal. While a tank cycles, it shows which stage the readings point to and calls it cycled only after two sessions in a row with ammonia and nitrite clear and nitrate present.

It's free with no in-app purchases, subscription or ads, for as many tanks as you keep. Signed out, everything stays on the phone; sign in only if you want it on another device. Export to CSV and JSON is free.

Limits: iPhone only (iOS 13 or later), English only, every value typed by hand (no strip scanning, no controllers), no species database, and no import of old logs beyond backdating readings one at a time.

Aquarium's log screen: one page of fields, previous values in grey, a timer beside each — Aquarium - Log Tracker: blank fields are not recorded as zero

AquaticLog: account-based, with controller data

AquaticLog has been around since 2013 and rates 4.2 from 409 ratings. Your log lives in an AquaticLog account, so it's on your iPhone, iPad and the web at aquaticlog.com. It logs the usual parameters and can pull hourly readings from a Neptune Apex, Hydros, AquaWiz or Seneye, including Seneye's NH3 and NH4. It keeps detailed livestock records with reef-safety and temperament, schedules retests for out-of-range results, and has Home Screen widgets.

Pick it if you run a reef or a high-tech tank with a controller, or want your log in a browser too. It needs iOS 18.1 or later and an account.

Aquarimate: species library and compatibility

Aquarimate costs $9.99 once and rates 4.4 from 626 ratings. It manages unlimited fresh and saltwater tanks, lets you add or remove parameters per tank, has unit converters and dosing calculators, a test timer, and charts that plot several parameters with your maintenance on one graph. Its Aquaribase library covers fish, coral, invertebrates and plants with compatibility advice, and it tracks expenses and equipment. It's available in 13 languages; the last update was in June 2025.

Pick it if you want a stocking library and compatibility checks in the same app as your log, and prefer to pay once.

Pocket Marine: for saltwater keepers

Pocket Marine costs $3.99 once and has the best rating here, 4.8 from 597 ratings. It's built for marine tanks: an encyclopaedia of over 800 marine fish, invertebrates and corals with compatibility notes, a testing journal for more than 30 parameters with trend graphs, dosing and water change logs, an inhabitants diary and reminders. It was last updated in April 2024.

Pick it if you keep a saltwater tank and want a species reference alongside the log for a small one-off price.

Fishi: fish and every other pet

Fishi rates 4.6 from 596 ratings and covers terrariums, aviaries and enclosures as well as aquariums. It monitors water parameters, gives insights on cycling progress, has feeding and maintenance reminders, and a library of hundreds of fish, reptile, insect, bird and small animal species. It runs on a monthly, quarterly or yearly subscription.

Pick it if you keep reptiles or other animals as well as fish and want them in one app.

Nitrify: for a tank that's still cycling

Nitrify is for freshwater keepers. You log ammonia, nitrite and nitrate, and it puts every test in a cycle stage (waiting on ammonia, the nitrite spike, finishing, cycled) with a Safe, Watch or Act call on each reading. The free version covers logging, the cycle stage, the safety verdict, one tank and iCloud sync; a one-time Pro unlock adds multiple tanks, reminders, custom schedules and an estimate of when the cycle will finish. Nothing is sent to a server. It needs iOS 26.2 or later.

Pick it if you're cycling your first freshwater tank and want a plain verdict on every reading.

AquaLens: camera scanning and photo ID

AquaLens scans test strips and liquid test kit results with the camera, identifies fish, plants, corals, algae and snails from a photo, and gives AI guidance based on your tank history. It also keeps the usual log, chemistry trends and maintenance timeline. It's free to start, with a Pro tier for advanced analysis, and rates 4.6 from 32 ratings.

Pick it if typing readings is what stops you logging, or you want to identify what's in your tank.

Reef Buddy: reef tracking with an AI assistant

Reef Buddy logs reef parameters (KH, salinity, pH, calcium, magnesium, nitrate, phosphate, silicate and more) with trends and automated insights, and syncs between iPhone and iPad. A premium tier adds Shrimpy, an assistant that analyses your data and tank photos and answers questions. It needs iOS 26 or later and rates 3.9 from 20 ratings.

Pick it if you keep a reef and want to ask questions about your numbers.

Which aquarium log app should you use?

You want a free, honest log for one or many tanks: Aquarium - Log Tracker.
You have a controller or want a web log: AquaticLog.
You want a species library and pay once: Aquarimate, or Pocket Marine for saltwater.
You won't type readings: AquaLens.
Your first freshwater tank is cycling: Nitrify.
You keep more than fish: Fishi.

FAQ

What is the best app to log aquarium water tests?

It depends on the tank. Aquarium - Log Tracker is free with no in-app purchases for any number of fresh or saltwater tanks; AquaticLog adds controller data and a web log; Aquarimate and Pocket Marine add species libraries for a one-off price; AquaLens reads test strips with the camera.

Is there a free aquarium log app with no subscription?

Yes. Aquarium - Log Tracker is free with no in-app purchases, subscription or ads, for unlimited tanks, and exports to CSV and JSON for free. Nitrify's free version covers one freshwater tank, with a one-time Pro unlock for more.

Which aquarium app can read test strips with the camera?

AquaLens scans test strips and liquid test kit results with the iPhone camera and keeps the readings in its log. Most other aquarium log apps, including Aquarium - Log Tracker, need readings typed in.

Which app tracks the nitrogen cycle in a new tank?

Nitrify puts every freshwater test into a cycle stage with a Safe, Watch or Act verdict. Aquarium - Log Tracker shows which stage the readings point to and calls a tank cycled after two sessions in a row with ammonia and nitrite clear and nitrate present.