Weekly entries written for a bottom dweller
A corydoras diary starts where the fish live: the bottom. Each week record ammonia, nitrite, nitrate, temperature, and pH, then add what happened at substrate level — how much sinking food went in after the main feeding, whether it was found and finished, and whether the sand or gravel was siphoned and how dirty the waste water looked. Note the group's size and any Cory added or lost. Corydoras are social, and a shrinking group changes behaviour tank-wide, so the headcount is a health entry, not bookkeeping. Finish with one line on the filter and any maintenance, since mulm and flow at the bottom respond directly to both.
Barbels, fins, and the dusk behaviour check
Corydoras whiskers — their barbels — erode in dirty water or on sharp substrate, so the diary needs a weekly barbel line: full and even, shortening, or stubby, checked when the fish rest on open sand in good light. Add fin condition and any redness around the belly or gills. Do the behaviour entry at dusk or after feeding, when corys are most active: a healthy group shoals, shuffles through the substrate, and makes occasional quick trips to the surface. A single cory sitting apart, motionless for long stretches, or breathing noticeably faster than the group is the exception the diary exists to catch early and date precisely.
Feeding competition: the entry most diaries miss
Corydoras starve politely in busy community tanks, so the weekly diary should state plainly whether sinking food survived the trip down. Record which food form was used — wafer, pellet, or frozen — where it was dropped, and whether mid-water tank mates intercepted it or the corys ate undisturbed. Note body shape monthly: rounded bellies across the group versus a few pinched individuals who always arrive late. If the log shows corys losing condition while tank mates thrive, the fix is feeding method and placement, and the diary provides the evidence. Log target-feeding experiments and their results so a method that worked is not forgotten by the next month.
How long corydoras entries remain useful
Keep the diary for the whole life of the group, which for well-kept corydoras can span many years and several tank generations of tank mates. The most recent two months steer weekly feeding and cleaning decisions, but the long record answers the questions that actually arise: when barbel wear first began and what substrate the tank held then, whether breeding behaviour follows water changes of a particular size, and how this group responded the last time a new species arrived. Deleting early entries deletes the substrate and stocking history that later problems refer back to, so archive the diary by group and let it accumulate.
Using the diary at the vet and at handover time
When several diary lines deteriorate together — barbels shortening, one fish isolating, breathing rates up, appetite down — test the water, siphon the substrate, and contact an aquatic vet with the diary ready rather than treating the tank blindly. Keep the weekly pages in one backed-up file with a sitter note explaining dusk feeding and the normal dash to the surface, so ordinary behaviour is not mistaken for distress. Holding that corydoras diary in KinsLe as a Pet Passport keeps the group's records together in one portable packet, complete for a vet visit, a tank upgrade, or a careful rehoming.