Celestial pearl danios are the boarders most likely to be failed by generic competence. A service can be excellent with guppies and goldfish and still lose these fish slowly, because everything about them is small-scale: marble-sized appetites, mouths that need food crushed fine, and a shyness that makes them stop feeding entirely when the housing feels exposed. Checking a service's knowledge means checking whether they think in this species' dimensions at all.
Ask what the fish will be fed, and how small
Start with food, and listen for size before variety. Celestial pearl danios take micro-pellets, crushed flake, and tiny live or frozen foods, and anything offered whole in standard community size simply goes uneaten while the water absorbs it. A service that knows the species will say the food is ground down, fed in very small amounts more than once a day, and targeted low in the water column where these fish hover. Ask whether they separate celestial pearls at feeding time; in a mixed boarding tank, faster fish clear the surface long before a shy danio commits to rising, and knowledgeable staff feed them in their own quiet water for exactly that reason.
Ask where the group will live during the stay
Housing questions reveal whether the service understands what the fish are like at home. Celestial pearl danios settle in dense planting with dim corners, gentle flow, and company of their own kind, kept as a group rather than split across tanks. Ask to see the actual boarding tank, not the showroom. Bare glass with bright light and nowhere to retreat is a genuine problem for this species, because a fish that feels exposed stops eating and fades over days in a way busy staff can miss. Bonus confidence if they mention keeping the water on the cooler side of the tropical range, which suits these danios and which a one-temperature-fits-all facility may not bother with.
Ask what else shares the water
Tankmates are where small shy fish lose boarding stays. Ask directly which species will be in the same system, and treat large, boisterous, or fin-nipping company as disqualifying no matter how good the rest of the answers sound. Celestial pearl danios are also small enough that a filter intake is a hazard, so ask whether intakes in the boarding tanks are sponged or screened. That single detail separates services that have actually kept nano fish from services that have merely heard of them, because everyone who has run a tank of fish this size has thought about the intake.
Ask how they would notice a problem
A fish the length of a fingernail does not announce illness theatrically. Ask what staff look for during the stay, and hope to hear about behavior rather than spots and lesions: fish that stop hovering in their loose group and sit on the bottom, males whose spotting and orange fins wash out, anyone not joining the drift toward food. Ask how often someone looks at the nano tanks specifically, and whether head counts happen, since a service that cannot say how it would notice one missing two-centimetre fish is telling you it would not. Prompt contact with you, with a photo, is the right escalation.
Weigh the answers as a set
No single question decides it; the pattern does. A service that answers in the species' own terms, small food, planted shelter, peaceful water, evening observations, earns your fish. One that keeps reassuring you that all tropical fish are basically the same has told you the important thing too. When you are drawing up the shortlist to interview, KinsLe's Pet Services Directory helps you find trusted local pet businesses and connect with them, which makes it practical to put these celestial pearl danio questions to more than one boarding service before you commit.