Corydoras spending resists a per-fish ledger because almost everything bought for them is bought for a group living on a shared tank floor. Sinking foods feed whoever reaches them, water changes serve the whole aquarium, and substrate care exists largely because bottom feeders live where waste settles. A workable method is one dated list for the cory group in three columns, food, water and substrate care, and equipment, with the group's size written beside each month's total so the numbers stay interpretable as the shoal changes.
The Sinking-Food Column and Its Honest Limits
Corydoras food spending centers on sinking wafers and pellets, granular foods that reach the bottom, and frozen offerings dropped in after lights-out. Some of that food is inevitably eaten by tankmates, and the log should admit it rather than pretend precision: mark purchases as mainly-for-corys or shared, and charge shared items once with a note. Over a quarter, the mainly-for-corys entries show the true cost of feeding the group, while the shared entries explain why the tank's overall food bill rose. Rotation purchases are the trap in this column; corys thrive on variety, but four open wafer containers bought in the same month is spending dressed as care.
Substrate and Water: Where Cory Care Money Concentrates
The care column for corydoras is dominated by the bottom of the tank. Water conditioner is used in larger volumes because waste concentrated at the substrate rewards regular, thorough changes and gravel or sand cleaning. Replacement filter media appears here more often in a well-fed bottom-feeder tank, as does the occasional bag of fresh sand to top up worn patches. Test supplies belong in this column as well, since water quality at the bottom layer is where a cory group feels neglect first. Reading this column across a few months usually reveals a steady, predictable rhythm, which is exactly what makes budgeting for this species straightforward once it is written down.
Group Size, Growth, and the Totals
Write the cory count beside every monthly total, because a group of six juveniles and a group of ten adults eat different amounts and foul the substrate at different rates. Note additions and losses on the same line, and mark the month juveniles moved up to adult portions of frozen food. That habit protects the budget review from false alarms: a food column that rises alongside a growing group is a plan working, not a leak. It also builds the honest answer to what a mature cory group costs monthly, which is the figure anyone considering a second group actually needs.
Using the Cory Log at Review Time
Quarterly, read the three columns as a story about the tank floor. Food steady, care steady, equipment rare is the settled pattern; a care column climbing without a group-size change points at feeding volume reaching the substrate faster than cleaning removes it. A food column spiking in treat purchases points at the keeper, gently. Keeping these spending notes with the tank's stocking list and purchase records means a cory group's cost history and life history explain each other, especially when the group is rehomed or expanded. KinsLe's Pet Passport holds that combined record well, keeping a cory group's monthly spending in the same packet as its identity and tank details.