One page, three lines, every week
The trick to spotting change in a betta is not more data but aligned data, so record water, food and behaviour together on a single weekly page. The water line carries temperature, ammonia, nitrite and nitrate from the week's test. The food line states what was offered, roughly how much, and the response — instant strike, interest after a pause, or food left. The behaviour line notes bubble nest activity, flaring, where he rests and how he greets the front of the tank. Three short lines, same order, same page. Because the lines sit together, a week where all three dip at once explains itself, and a week where only behaviour dips points away from the water.
Building his baseline before you need it
A trend is only visible against a normal, so the first month of recording a betta's habits is really baseline-building. Learn his pattern and write it down plainly: he nests after water changes, he rests on the broad leaf at night, he eats eagerly in the morning and less at night, his temperature sits steady at its usual mark. Later entries are then judged against him, not against an internet description of a generic betta. This matters because individuals differ enormously — one betta's quiet week is another's ordinary week — and your recorded baseline is the only version of normal that applies to the fish in front of you.
Feeding records that catch the slow fade
Appetite is the betta sense that fades first and is noticed last, which is why the food line records response as carefully as amount. Note refusals even when everything else looks fine, and note the day a favourite food stops working. A pattern of eating well for two days then skipping one, written down over a month, is a genuine finding to take to an aquatic vet; the same pattern noticed vaguely is just unease. Record treats and fasting days as well, so the line stays honest. Paired with the water line, the feeding record separates a fish put off by a temperature slide from a fish whose problem lies elsewhere.
Behaviour trends worth their own words
Write behaviour in observable words — nested, flared at the mirror of his own reflection, patrolled, hid behind the filter, sat on the gravel — rather than judgements like 'seems sad'. Observable words can be compared across weeks, which is the whole purpose. Watch especially for losses: the nest that stops being rebuilt, the greeting at the glass that stops happening, the resting leaf abandoned for the floor. Bettas also change with age, and a graceful slowing across a year of pages is a different story from a change across a fortnight. The record lets you tell those two stories apart instead of worrying over both.
When the page says it is time for a vet
Take the record to an aquatic vet when the lines move together and stay moved: appetite down across several entries, behaviour shrinking, fins or body changing, with water readings that do not explain it — or when anything sudden appears, such as rapid breathing, pineconing scales or a fish unable to right himself, which should never wait for a trend. Bringing the weekly pages turns the consultation from guesswork into review. Keeping those pages in KinsLe's Pet Passport holds a betta's records together in one portable packet, so his baselines and trends are ready to share whenever a vet, sitter or new keeper needs the full picture.