Aquarium Manager: a water test log and cycling coach for every tank

The useful ones do three things: store every reading so you can see a trend rather than a single number, tell you plainly whether the tank is cycled, and remind you about water changes before they slip. Aquarium Manager is built around exactly that — a water test log for ammonia, nitrite, nitrate and pH charted over time, a cycling coach that reads those numbers, and a maintenance schedule. It is free on iOS and Android.

Usually several weeks. The bacteria that convert ammonia to nitrite, and nitrite to nitrate, have to multiply until they can process everything the tank produces in a day, and that commonly takes around four to six weeks in a new setup. Warmth, surface area in the filter and seeded media from an established tank all speed it up. Testing every day or two is the only way to know where you actually are.

Ammonia comes from fish waste, uneaten food and decay, and is toxic even in small amounts. Bacteria turn it into nitrite, which is also toxic because it interferes with the fish's blood carrying oxygen. A second group turns nitrite into nitrate, which is far less harmful and builds up slowly. In a cycled tank ammonia and nitrite should both read 0 ppm, with nitrate present and kept down by water changes.

The tank is ready when it can process a dose of ammonia within about 24 hours and still test 0 ppm ammonia and 0 ppm nitrite, with nitrate showing on the test. One clean result is not enough; you want that pattern to hold for several days. Then stock slowly, a few fish at a time, so the bacteria colony can grow to match the new bioload instead of being overwhelmed.

A partial change of roughly a quarter of the volume every week or two suits most freshwater community tanks, but the tank decides, not the calendar. Rising nitrate means change more water or more often; heavily stocked and heavily fed tanks need more than lightly stocked planted ones. Match temperature and treat tap water for chlorine before it goes in, and never strip and scrub the filter media at the same time.

New tank syndrome is what happens when fish are added before the nitrogen cycle is established: ammonia climbs with nothing to consume it, nitrite follows, and the fish are poisoned by their own waste. The reliable way around it is fishless cycling — dose an ammonia source into an empty tank and wait until ammonia and nitrite both fall to zero within a day. Testing throughout is what tells you where you are.

Yes. Aquarium Manager is free to download from the App Store and Google Play, and it is rated 4+. It covers logging your tanks, water test history, the cycling coach, the maintenance schedule, the species guide and compatibility checks. Terms of use and the CoddyKit privacy policy are both linked from the store listing if you want to read them before installing.

Yes. A tank can be set up as freshwater, saltwater, planted or reef, and each one keeps its own livestock list and its own reading history. Reef and planted keepers are one of the groups the app is aimed at, because those tanks are where slow chemistry drift does the most damage — the charted history is what makes a gradual change visible before it turns into a crash.

Not definitively, and it should not be treated that way. You can photograph a sick fish for informational guidance, or describe the symptoms for hobby-level troubleshooting of common tank problems, and both are meant as a starting point rather than an identification. For a sick or valuable animal, consult an aquatic vet. In practice, checking your water first solves a large share of problems that look like disease.

Yes. Aquarium Manager records and charts the readings you take; it cannot measure the water itself. You need your own test kit for ammonia, nitrite, nitrate and pH, and the app turns those numbers into a history, a tank health score out of 100, and a cycling read on whether stocking is safe. Without regular testing there is nothing for the trend line to show.