A weekly change suits peppered corydoras
Peppered corydoras do best with a partial water change once a week in a normally stocked home aquarium. Replacing roughly a quarter of the water keeps dissolved waste from building up while avoiding the sudden shift a very large change can cause. If the tank is heavily stocked, the group is large, or test results keep climbing between changes, move to smaller changes twice a week rather than letting a single weekly change grow bigger.
These are not fish that live in the middle of the water. Peppered corydoras spend their day shuffling along the bottom, sifting the surface of the substrate for food with their whisker-like barbels. That puts them in closest contact with the layer where uneaten food and droppings settle.
Why the bottom matters more than the surface
A change that only dips water off the top misses the part of the tank a cory actually inhabits. Use a gravel siphon during the weekly change and work slowly across the substrate, lifting debris from around plants, caves, and feeding areas where pellets land. Go gently near the fish themselves. Corydoras startle easily and will dart away from a fast-moving tube, and their barbels can look worn when they are constantly pushing through dirty, coarse gravel.
Refill with dechlorinated water brought close to the tank temperature before it goes in. Pour it in slowly, ideally over a plate, a hand, or a decoration that breaks the flow, so the current does not blast the bottom and stir settled waste back into the water the fish are breathing.
Reading the group between changes
Watch how the school behaves in the days after a change. Healthy peppered corydoras forage in loose company, rest together in shaded spots, and make occasional quick trips to the surface. A group that goes quiet, stops rooting through the substrate, crowds at the surface repeatedly, or shows shortened, ragged barbels is telling you the bottom conditions have slipped, even if the water above looks clear.
Test the water when behaviour changes rather than guessing. Rising waste readings mean the routine needs tightening first: check that nobody is dropping in extra food that sinks uneaten, confirm the filter is running properly, and shorten the interval between changes for a while. If several fish look unwell, lose their appetite, or develop redness around the barbels and belly, contact an aquatic vet or an experienced fish shop promptly rather than simply changing ever larger volumes of water.
Keeping the weekly rhythm from drifting
Pick a fixed day, keep the siphon, bucket, and dechlorinator together, and do the cory tank before any showier tanks that tempt you to rush. Note what you removed, how the substrate looked, and whether the barbels and fins looked clean, so the next person can compare rather than start from memory.
That shared routine is easier to hold when it is written down per pet, and in KinsLe, Care Teams let you assign the weekly siphon, refill, and bottom check for the peppered corydoras to a named helper, with each completed task marked by a timestamp.