One entry per arrival, written on the day it happens
A fish's paperwork life should start before it leaves the bag. Create the entry on arrival day with the facts that are freshest then and impossible to reconstruct later: the species and how many, the source named precisely — which shop, which breeder, which fellow keeper — and the date. Add what you noticed at purchase: the fish active and feeding in the shop tank, any tankmates there that looked unwell, the condition of the fish on release into quarantine. These observations feel like trivia on day one; they become the key evidence if the fish sickens a week later, because they help separate a problem the fish arrived with from one it met in your water.
The quarantine dates are the spine of the entry
Quarantine only works as a record if its dates are exact. Log the date the fish entered the quarantine tank, and keep the entry open — not filed away — until the fish leaves it. The two dates, in and out, prove the quarantine actually ran its full course rather than being shortened by impatience, which is the most common way quarantine fails in practice. If a fish is moved early because the quarantine tank is needed or a problem forces your hand, log that too, with the reason: an honest short quarantine on paper is worth far more than a fictional full one, because it tells you how much trust to place in the all-clear.
Brief daily notes while the fish is in quarantine
Quarantine notes do not need to be essays — a line a day is plenty — but they should cover the same three things each time: is the fish eating, and what; how is it behaving compared with yesterday; and anything visible on the body, fins or gills that was not there before. Record any treatment you give in the same entry, with the product name copied from its bottle and the dates it ran, rather than in a separate treatment log where it can become separated from the fish it concerns. Patterns are what you are collecting: a fish that eats from day two and stays bright is a different proposition from one whose appetite fades on day five, and only the daily line shows the turn.
Close the entry with the move, and keep it findable
When the fish graduates, close the entry properly: the date it moved, which tank it went into, and a final line on its condition at the move. Then transfer the essentials — species, number, source, arrival date — onto that tank's stocking record so the population count stays true. Keep the full arrival entry filed by date or by species where you can find it again, because the questions it answers tend to arrive months later: where did that strain come from, which batch did the sick fish belong to, did the fish from that source do well last time? A source that appears in your log beside healthy fish, again and again, earns your repeat custom; the log is how you know.
Sources, batches and the pattern across entries
Read together, arrival entries become a map of your supply chain. Fish from one shop thriving while fish from another repeatedly struggle in quarantine is not proof, but it is exactly the kind of signal that should steer where you buy — and you can only see it across entries, never from memory of individual fish. Kept in a KinsLe Pet Passport, the arrival and quarantine records sit with the stocking sheets they feed, so each tank's population has a documented history: every fish traceable to a source, a date and a quarantine properly served.