Log every water test in seconds

Most aquarists do not lose fish because they never tested. They lose fish because they tested three weeks ago, wrote the number on a sticky note, and cannot remember whether nitrate was 20 or 40 when they changed water. FishTank Diary exists to close that gap: one screen, five fields, about twenty seconds.

What you can log

• pH — and enough room in the notes to record whether you measured with a liquid kit, a strip, or a probe.
• Ammonia — the reading that tells you whether your biofilter is keeping up.
• Nitrite — the second half of the cycle, and the one people stop checking too early.
• Nitrate — your water-change trigger, and the number that tells you whether your schedule actually matches your stocking.
• Temperature — logged next to the readings so a heater failure shows up as a pattern, not a surprise.
• Any custom parameter you add, so saltwater and planted-tank keepers are not stuck with five fields.

Reuse your last checklist

The slowest part of logging is retyping the same five labels. The app remembers your last test for that tank and pre-fills the entry, so you only change the numbers that moved. If nothing moved, saving takes two taps.

What happens when a number looks off

The dashboard flags readings that are outside the range you set for that tank, and surfaces them on the Today screen. It does not diagnose disease, and it will not tell you to dose anything — it tells you what you recorded, when, and what changed since the last test. That is the part a human is bad at remembering and an app is good at.