A log built around seasons, not scales
Rice fish — the medaka kept in aquariums and outdoor tubs for generations — are far too small to weigh usefully, and too hardy to need fussy monitoring. What they reward is a simple, regular health log, because their lives run on rhythm: breeding in the warm, bright months, slowing as the water cools, and schooling through it all. Written weekly, a few lines capture that rhythm and flag the fish who falls out of it. Judging condition is visual — body depth from above, vigour at feeding, and spawning behaviour — and a log gives those impressions dates, which is what turns them into evidence.
Viewing from above is the medaka keeper's advantage
Rice fish were selected for centuries to be appreciated from above, in bowls and tubs, and that viewing angle happens to be the best one for condition checks. From overhead you can compare every fish in the school at once: a healthy medaka shows a smooth, gently rounded outline, while a fish losing condition narrows, especially behind the head. Make the weekly entry at feeding, count the school, and note each fish's outline as they gather. This top-down census is quicker and less disturbing than netting anyone, and for outdoor fish it doubles as a predator and escape check after storms or visits from neighbourhood wildlife.
Spawning entries anchor the breeding season
During the breeding months, females carry clusters of eggs attached beneath the body for part of the morning before brushing them off onto plants or spawning mops. Log which weeks you see eggs being carried, whether egg-covered plants were moved or left, and when fry first appear, because this species' breeding is steady rather than dramatic and easy to under-record. A season with no eggs at all, in fish that bred the previous year, is meaningful information about age, condition, or water temperature — but only if last year's pattern is written somewhere to compare against. Note males' colour too, as breeding males deepen in tone and display to females.
Temperature belongs in every outdoor entry
For rice fish kept outside, temperature is the single most useful number in the log. Record the water temperature at each check, heatwave behaviour such as gathering at the surface in the early morning, and how the group responds to cold snaps, including when feeding naturally falls away in cool water. Medaka tolerate a wide range, which is exactly why the log matters: tolerance hides slow stress, and a written run of temperatures beside appetite notes shows whether a quiet week was ordinary winter behaviour or the start of losses. Indoor keepers should log heater faults and room-temperature dips the same way, briefly.
When the record says to intervene
Contact an aquatic veterinarian when a rice fish stays thin despite eating, when several fish develop curved or stunted shapes, when you find repeated deaths across a few entries, or when spots, raised scales, or persistent surface-sitting appear in more than one fish. Test the water the day you notice a group change and write the readings into that entry — outdoor tubs collect leaf litter and rain overflow that shift conditions quietly. Because medaka are usually kept as a group, the log's headcount history is often what reveals a slow decline in numbers that daily viewing completely missed.
One seasonal record, kept straight
Rice fish notes sprawl across years if the colony is kept well, and the comparisons that make them valuable are year against year. Holding the entries in KinsLe's Pet Passport keeps your rice fish's temperatures, spawning weeks, and group photos in one packet, so each new season's log starts from the last one's facts.