Corydoras are so placid that a boarding service can neglect their real requirements while appearing to care for them beautifully. They will not beg, jump, or pine visibly if the substrate is wrong, the group is split, or no food ever reaches the bottom; they simply decline quietly over the stay. Testing a service's corydoras knowledge means asking about the unglamorous details this species actually lives by, all of which happen at floor level.
Ask whether your shoal stays together
Corydoras are social to their core and rest, forage, and gain confidence as a group, so the first question is whether your fish will be housed together as the shoal they are, in a tank of their own or with peaceful company. A service that proposes splitting them across whatever tanks have space, or boarding them singly, does not understand the animal in front of it. Ask, too, whether other bottom dwellers will share the floor, because a corydoras trying to rest among pushy loaches or a territorial pleco spends its holiday stressed rather than settled. Their own kind, in their full number, over a quiet floor: that is the answer you are listening for.
Ask what is on the bottom of the tank
Substrate is a welfare issue for corydoras, not a decorating choice, because they push their whiskered faces into it at every meal. Sharp or coarse gravel wears and damages those barbels, and damaged barbels open the door to infection. A knowledgeable service houses them over sand or smooth, fine gravel and will say so without being led. While you are looking at the floor, ask how it is cleaned: waste settles exactly where corydoras live, so the service should describe regular siphoning of the substrate in boarding tanks, not just water taken from the top.
Ask how food reaches the bottom
Surface feeding is the classic corydoras failure. Flake sprinkled for mid-water fish may be eaten entirely before a scrap descends, and a cory tank can look fed while the catfish go hungry. A service that knows the species feeds them directly: sinking pellets or wafers placed on the substrate, ideally toward evening when corydoras liven up, in enough separate spots that the whole group eats without crowding. Ask whether bottom feeders are fed as their own task on the daily round or simply included in the general scatter. You want the former, described as routine rather than as a special favor arranged for you.
Ask what they make of worn barbels and still fish
Give the service a scenario: one of your corydoras is sitting motionless and its whiskers look short. Staff who know the species will connect those signs to conditions at the substrate, talk about testing the water and checking the floor of the tank, and want the fish somewhere clean and quiet while they contact you. Staff who do not may shrug that catfish rest a lot, which is true and beside the point, or reach for a general tonic, which tells you their troubleshooting is guesswork. Also ask about their water change routine for the bottom tanks, since corydoras react poorly to large, sudden changes; steady small maintenance is the practiced answer.
Compare answers across more than one service
Corydoras knowledge is common enough that you can afford to be choosy, and the differences between services show up fast once the questions turn to floors, groups, and sinking food. Take notes on each conversation; the service that volunteers details you did not ask about, like keeping a spare cave-free open patch of sand for resting, is usually the one that keeps these fish at home. To build that comparison list, KinsLe's Pet Services Directory lets you find local pet boarding businesses and connect with them, so your corydoras questions reach several services before the shoal spends a night in anyone's care.