Keep the digging, lower the climbing
Deep digging bedding stays, but climbing comes down, in the adjusted home of an elderly fat-tailed gerbil. This desert species lives to dig, and an old gerbil will still work his bedding happily at floor level; what age takes away is the safe climbing, so lower any shelf, remove stacked levels, and make sure nothing heavy can topple into a burrow.
Keep the digging depth generous but the structures simple. A cork tube or low hide half-buried at floor level gives an elderly fat-tail the enclosed sleeping space he wants without asking him to climb for it, and his tunnels stay in the lower bedding where a collapse is a nuisance, not an injury.
Food, water, and sand at burrow level
Everything an elderly fat-tailed gerbil needs daily should sit beside his burrow entrance. A low, heavy water dish or a bottle fixed at standing height, his food scattered in the nearby bedding, and a sand bath in a container with a low lip he can step over together remove every climb and long trek from his routine.
The sand bath matters beyond grooming. Rolling in sand keeps a fat-tailed gerbil's coat in condition, and an older animal who stops bathing because the dish became hard to enter will look scruffy quickly — a visible clue that access, not health, may be the first problem to fix.
Read the tail as part of his daily check
The tail is a health gauge unique to an elderly fat-tailed gerbil, because this species stores fat reserves there. A tail that stays plump while his activity gently declines is reassuring; a tail that visibly thins, especially alongside eating less, is an early warning worth writing down and weighing against his weekly weight.
Weigh him weekly in a small container and note tail condition in the same line. Between the two records you get a clear picture of whether this senior is holding his reserves or drawing on them, and that distinction shapes what his vet will advise.
Warmth, quiet, and a steady routine
A warm, steady environment suits an elderly fat-tailed gerbil, whose desert origins make cold a real strain on an aging body. Keep the tank away from draughts and cold windows, in a room with a stable temperature, and let his day run undisturbed — fat-tails are most active in bouts, and an old animal's rest between bouts should be protected.
Spot-clean rather than fully stripping the tank. A complete bedding change erases the scent map an elderly gerbil navigates by and forces expensive rebuilding work on a body with less to spare, so refresh sections at a time and leave his main burrow corner for last.
When adjustments stop being enough
Seek a vet experienced with exotic small mammals if an elderly fat-tailed gerbil's tail thins quickly, if he stops digging and stays hunched at the surface, or if his breathing becomes audible or laboured. Surface-sitting in a burrowing species is itself a sign something is wrong, because a well fat-tail spends much of his day below ground.
Bring your notes on weight, tail condition, and activity when you go. Keeping that record in KinsLe's Pet Passport gives the vet the trend for this elderly fat-tailed gerbil rather than a single day's snapshot, and trends are what senior care decisions are made from.