Ask about light feeding for fish that breed as they eat
Ask a sitter whether they will feed your guppies lightly and exactly as measured. Guppies are enthusiastic feeders with small bodies, and a community of them will swarm any amount of food, which makes heavy feeding look harmless while it quietly loads the water. Ask if they will give the amount you portion out, spread it so shy fish get a share, and resist feeding the fry extra meals beyond the schedule you set. Explain that guppies graze algae and pick at surfaces between feeds, so a guppy tank is never truly unfed. A sitter comfortable with that restraint will keep the water steadier than one who feeds on demand.
Ask the fry question before the fry arrive
Ask a guppy sitter the fry question before any fry arrive. A female guppy can give birth during almost any absence, and a sitter who finds tiny fish in the plants may either panic, try to rescue every one into a jug, or assume something has gone wrong. Tell them plainly what your setup expects: whether fry shelter in your floating plants and grow on in the tank, whether you use a separate nursery area, and what, if anything, they should do beyond leaving the newborns alone. Also ask them not to move a heavily pregnant female, because chasing and netting her at that stage risks the very fry they are trying to protect.
Ask whether they will keep males, females, and numbers straight
Ask whether the sitter can keep your guppies' group straight. In a mixed tank the balance of males to females matters, because males court persistently and a female singled out for attention can become stressed and hide. Ask the sitter simply to notice and report that kind of change rather than rearrange the group themselves, and to count roughly at feeding time so a missing fish is spotted early. If you keep a single-sex display tank, say so clearly, because a sitter who buys a few females as a surprise gift has changed your population and your water load in one kind gesture.
Ask about additions, chemicals, and helpful cleaning
Ask a guppy sitter to add nothing and clean gently. The risky sitter moves for a small, lively tank are familiar ones: a splash of someone's water treatment, a scrubbed filter that removes the bacteria the tank depends on, a new plant dropped in unrinsed, or tap water topped up without the conditioner you use. Ask directly whether they will stick to the items on your shelf and the steps on your list, and check the filter and heater or light timer by looking rather than dismantling. Guppies forgive small slips, but a tank kept boringly consistent is the real goal of any handover.
Ask how they will report a quiet guppy
Ask how the sitter will report a guppy that changes. One fish hanging at the surface, hiding behind the filter, or missing the feed while the rest swarm is worth a same-day message and a photo, because in a fast-moving group a single quiet fish is easy to overlook for days. Agree that they will not attempt treatments or water experiments on their own judgement, only describe, photograph, and contact you or your named backup. When the conversation is done, recording the handover in KinsLe through Care Pass puts the guppies' routine and key details in the sitter's hands for just the length of your trip.