Choosing sand that is safe to roll in
The bath is only as safe as what fills it, and the label to avoid is "dust". Chinchilla-style bathing dust is milled far too fine for dwarf hamsters and gerbils — it hangs in the air, coats their airways, and irritates eyes and noses. What you want is sand: plain children's play sand, washed and dried thoroughly at home if it arrives damp, or a pet sand sold for reptiles provided it is undyed and contains no added calcium. Run it through your fingers before it goes anywhere near the cage: it should feel like beach sand, soft but granular, and it should never puff into the air when poured. If a product clouds when you shake the bag, it fails the test whatever the packet calls it.
Setting up the bath so it stays a bath
Choose a heavy ceramic or glass dish with a low side — heavy enough that a Roborovski hamster rolling at full enthusiasm cannot tip it, wide enough for a complete roll with room to spare. Sink it slightly into the bedding so the rim sits near bedding level and nobody launches off an edge. Fill it an inch or two deep: enough to coat a coat, not enough to bury anything in. Position it away from the water bottle, since wet sand clumps and gets refused, and for hamsters keep it clear of the food-store corner. Roborovski dwarfs are the great bathers and can keep a bath permanently; other dwarf hamsters and gerbils may prefer it offered several times a week and removed between sessions.
The eating question, answered honestly
A new bath gets investigated by mouth first — expect the opening session to include deliberate-looking mouthfuls, and pouches bulging with sand carried off and spat out in a corner. This is sampling, not dining, and it fades within a few sessions as the sand becomes familiar furniture; the small amounts a healthy animal swallows in the process pass through without incident. What should end the experiment is an animal who keeps eating sand session after session, or one who pouches it constantly instead of rolling — take the bath out and mention the habit at his next vet visit, because persistent sand-eating can ride along with a diet or health issue worth ruling out. Never fill the bath with anything scented or vitamin-boosted to make eating it seem safer; the answer is plain sand or no bath.
Sifting and storing so nothing is wasted
After each use, pour the sand through a fine kitchen sieve or mesh scoop: droppings, stray seeds and bedding shake out, and the cleaned sand goes straight back in. Gerbils in particular may adopt the bath as their toilet — which is a gift, since it concentrates their waste in the one siftable place — and a bath used that way simply needs sifting more often. Replace the fill completely when sifting stops restoring it: a lingering odor, clumping that is not from a spill, or a grey, tired look after weeks of honest service. Store the spare sand dry in a sealed tub; damp stored sand turns musty and will be refused by animals whose noses are far better than yours.
KinsLe Family Sharing lets the owner share a profile for each animal with selected relatives.