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Free Printable Aquarium Water Quality Log (PDF)

This is a free, one-page printable aquarium water quality log in PDF format. Each row is one test session: date, water temperature, pH, ammonia (ppm), nitrite (ppm), nitrate (ppm), and general hardness (GH). Works for freshwater, planted, and saltwater tanks. Water chemistry changes gradually and silently — a written log is how experienced fish-keepers catch problems before livestock is lost. Not veterinary advice.
Download the PDF — free No sign-up. No email. Print and go.

How to use this sheet

  1. Print the PDF and keep it near your testing area or stuck to the side of the aquarium cabinet.
  2. Run your water tests and log each result in the corresponding column — one test session per row.
  3. In the Notes column, record any water change done: volume replaced, conditioner used, or any treatment added.
  4. Keep an eye on ammonia and nitrite — in a cycling tank or after adding fish, these are the danger columns. Both should read zero in an established tank.
  5. If a fish shows stress or illness, look back at the previous two weeks of logs — a pattern almost always precedes a problem.

Questions

Is this log really free?

Yes. The PDF is free to download and print — no sign-up, no email.

How often should I test my aquarium water?

For a cycling tank: daily or every other day for ammonia and nitrite. For an established stable tank: weekly pH, nitrate, and temperature; monthly for the rest. High-bioload tanks and planted tanks with CO2 injection need more frequent monitoring.

What are safe ammonia and nitrite levels?

Any detectable ammonia or nitrite in an established tank is a problem — both should read 0 ppm. Nitrate up to 20 ppm is generally tolerated by most fish; under 5 ppm is preferred for sensitive species and planted tanks.

Is there an app version?

Yes — Coralog for iPhone logs aquarium and reef parameters with trend charts and alerts. Core is free, no account needed, and your data stays on your device.

Want the log to analyze itself?

Coralog for iPhone tracks the same things in seconds and shows you the patterns — free core, no account, and everything stays on your device.

Download on theApp Store