Try the tool above
Use the free tool at the top of this page first, then read the guide below to understand the result and use it well. Fish cannot tell you when they feel ill, so small behaviour changes are often the only early warning you get. This log lets you record behaviour, appetite, and appearance with dates, building a simple history you can read back when something changes, instead of relying on memory.
How to use it
Start by entering the numbers the tool asks for, using real measurements where you can, then press the calculate button and read the result box carefully. Check the result against common sense for your own setup, adjust one input at a time if the answer surprises you, and use the result as a daily plan rather than a one-off number.
Worked example
For example, logging Bubbles as active with a good appetite on 28 October gives you a baseline to compare against later. If the same fish is logged as lethargic with refused food a week later, the change is clear and dated, not just a feeling.
How the calculation works
The tool uses a simple, transparent rule based on the numbers you enter, so you can check the answer by hand if you ever doubt it. It does not guess, hide its working, or pretend to know more than the inputs allow, and that honesty is deliberate, because a pet care plan you can follow matters more than a complicated formula you cannot trust. If you change one input, such as weight, fish count, or tank size, the result moves in the direction you would expect, which is a good quick check that you typed the numbers correctly.
Why this matters
A dated record turns vague worry into useful evidence, because you can see whether a fish stopped eating yesterday or has been hiding for a week. If you ever ask a shop or vet for help, that timeline is far more useful than saying the fish looks unwell.
Keep the routine going
The best plan is the one you actually repeat, so tie the result to something you already do every day, such as the morning feed, the evening tidy, or the weekly shop. Keep the tool result visible for the first two weeks, note any day you miss, and do not restart from scratch after a missed day, because one missed day matters far less than giving up the routine entirely and starting again next month.
Three tips that help
Log at the same feeding time each day, because behaviour right after feeding looks different from behaviour in the morning. Note water changes and new fish in the same log, since those events often explain a behaviour change the next day. Photograph anything unusual, such as spots or torn fins, because photos show change over days better than words alone.
Common mistake to avoid
Never guess a diagnosis from one log entry, because this tool is for record-keeping only and real illness needs proper advice and water testing.
Frequently asked question
What should I record about my fish health? Date, fish name, behaviour, appetite, and appearance notes, kept in order, so trends over days and weeks become visible in this log.
Put the result into practice
Save or print your result, put it where the person who feeds or cares for your animals will see it, and review it whenever weight, fish count, or tank setup changes. Small steady routines beat perfect plans that nobody follows, so keep the plan simple, repeat it daily, and adjust slowly when the numbers tell you something has changed.