TestwaterAquarium test log for iPhone
How Testwater compares
What sets it apartWith Plus, it works out your doses: millilitres of reef supplement from your latest test, or grams of dry fertiliser for a planted tank. None of the other apps here lists a fertiliser calculator.
Testwater is a water test log for freshwater, planted, marine and pond tanks, coming soon to the App Store. Each reading sits against your own target range, with no limit on readings and no account. Plus adds more tanks and works out reef and planted doses.
Why choose Testwater
- Unlimited readings, free for one tank. Each against your own target range, marked High or Low when it’s outside.
- Every parameter you test. Starting sets for each kind of tank, from alkalinity, calcium and magnesium to nitrate, phosphate and CO2, plus your own.
- No account. Your readings stay on your iPhone, in your iPhone’s own backups and in the files you export.
- Bring your spreadsheet. CSV import and export, and a backup file, on every plan, plus maintenance tasks with reminders.
Side by side
From each app’s UK App Store page and its developer’s site on 19 October 2026. “Not listed” means we didn’t find it there.
| Feature | Testwater | AquaticLog | Fishkeeper | Coralog |
|---|---|---|---|---|
| Price on the UK App Store | Free for one tank; Plus £1.99 a month or £12.99 a year | Free for one aquarium, with unlimited readings for the first 30 days (what follows isn’t listed); Pro £4.99 a month, £39.99 a year or £149.99 once | Free; no in-app purchases listed | Free; Premium £2.99 a month or £19.99 a year; lifetime £39.99, once |
| Works out a dose for you | Yes, with Plus: reef supplements in mL from your product’s label; planted dry fertiliser in grams (the Estimative Index, EI, or your own targets) | Not listed; it logs your doses | Not listed | Reef only, with Premium: alkalinity, calcium and magnesium |
| Where your readings are kept | On your iPhone; nothing sent to us | In your AquaticLog account | On Fishkeeper’s servers | On your iPhone |
| Works without an account | Yes | No: your log lives in your account | No: it opens on Sign in or Create An Account | Yes |
| Import and export your readings | CSV import and export, and a backup file, on every plan | ICP lab reports in, with Pro; a text snapshot to copy out | Not listed | CSV export, free |
| Records your fish, corals and plants | No: water tests, maintenance tasks and doses only | Yes, with photos | Yes, with a livestock library | Yes, with photos |
What you pay. Testwater Plus is £1.99 a month or £12.99 a year, for every tank and the dosing maths. AquaticLog’s Pro is £39.99 a year and Coralog’s Premium £19.99 a year; Fishkeeper is free, with an account.
Another app may suit you better if
- you want every tank free and don’t mind an account: Fishkeeper is free for any number of aquariums and ponds.
- you want your log on an iPad, Android or the web too: AquaticLog keeps it in your account.
- you keep only reef tanks and would rather pay once: Coralog’s lifetime purchase, with its reef dose calculator, is £39.99.
What people ask for, and what Testwater does
A log that keeps taking readings
Keepers who have logged for years ask for an app that never caps free readings. Testwater has no limit on any plan.
Help with the dosing maths
For reef supplements Testwater Plus works the dose out from your product’s label and your latest test, with the working shown. For a planted tank it gives the grams of each dry fertiliser for EI or your own targets. Both ask you to check with your test kit before and after dosing.
Questions
Which aquarium log app works out reef and EI doses?
Testwater Plus works out both: millilitres of reef supplement from your latest test, and grams of each dry fertiliser for EI or your own targets. Coralog’s Premium lists a reef calculator. We didn’t find a fertiliser calculator listed for AquaticLog, Fishkeeper or Coralog on 19 October 2026.
How does Testwater work out a reef dose?
You type in your own product’s figures from its label; Testwater knows no brands. With your latest reading, your target and your tank’s volume, it spreads a big raise over days, never more than the daily rise you set, with the working shown. Check with your test kit before and after dosing.
Is there an aquarium water test app without an account?
Testwater needs none: your readings stay on your iPhone. Coralog also lists no account; AquaticLog and Fishkeeper use one.
How much is Testwater?
It’s coming soon to the App Store. One tank is free with unlimited readings; Plus is £1.99 a month or £12.99 a year in the UK (elsewhere the App Store shows the price in your currency before you confirm), with no free trial.
What happens if I stop paying for Plus?
Nothing is deleted. Your oldest tank keeps working as on the free plan; the others become read-only, still there to view, export and delete, and dosing locks until you subscribe again.
Checked 19 October 2026 on the UK App Store and each developer’s own website. Testwater isn’t on the App Store yet; its column describes the app as built. Other apps change; if something here is out of date, tell us.