Quarantine only works as observation. The new fish lives alone for a period so you can watch it closely, learn its normal patterns, and notice any change while it is still separated from the main tank. A daily log turns that watching into evidence: five entries a day, in the same order, in the same plain words, from the first day to the last.
Appetite and Behaviour Entries
Write appetite first. Note what was offered, in your usual measure, and how much was eaten: all of it, part of it, or none. New fish often refuse food for a day or two after a move, so the entry matters as a trend rather than a daily verdict. Note the time of feeding too, since appetite read at a consistent time compares fairly across days.
Behaviour comes next. Record where the fish spends its time: out in the open, near the filter, low by the substrate, or hidden in decor. Record how it swims: steady and level, tilted, darting, or rubbing against surfaces. Note its response when you approach the glass. A fish growing bolder across the week writes a very different log from one retreating further each day, and both patterns only show if you write them down daily.
Breathing, Waste, and Marks
Observe breathing at rest, with the tank undisturbed and your hands away from the glass. Note whether the gill movements look calm and even or fast and laboured, and whether both sides move alike. Breathing read during feeding or netting tells you nothing, so take this entry before you feed or clean.
Waste earns its own line: its colour, whether it holds together or trails, and whether it looks like the food going in. Waste changes with diet, so note any food change beside the waste entry to explain the difference. Marks complete the five: any spot, patch, pale area, raised scale, or fin edge change you can see, described by position, such as left flank or tail fin, so tomorrow's entry can be compared exactly.
Photograph the fish on any day something looks different from the day before, in the same light where you can. Enter the day's water test results beside the five entries, and record water changes and feeding times on the same page. This log is observation only: it records what you see, and it makes no claim about causes or cures.
Reading the Log and Deciding
At the end of the quarantine period, read the whole log from the start. You are looking for stability: appetite settled into a pattern, behaviour consistent, breathing calm across the entries, waste steady, and no new marks appearing in the later entries. A log that shows a change mid-period, followed by entries returning to the earlier pattern, is still useful information; note it and let the fish complete further settled days before deciding.
If the log shows a persistent change instead, such as repeated food refusal, worsening marks, or laboured breathing across several days, keep the fish separate and seek advice from an aquatic vet or a knowledgeable specialist shop, taking the log with you. The daily entries give that adviser dates, sequence, and detail that a worried summary cannot.
Do not shorten the observation because the first days look calm; some changes only appear once the fish has settled and fed for a while. Equally, do not extend quarantine endlessly without a reason recorded in the log itself.
KinsLe keeps each day's five entries in order inside a Pet Passport record, keeping the completed quarantine history attached to the fish's profile when it finally joins the main tank.