The minimum for an adult bumblebee goby
An adult bumblebee goby needs at least ten gallons, and the honest minimum rises with the number of gobies you keep. One fish barely exceeds an inch and a half, so ten gallons sounds generous until you remember that this species lives on the bottom and measures its world in claimed hiding places, not in open water. A long ten-gallon footprint with sand, small caves, shells, and broken plant cover lets a handful of gobies each hold a spot. Twenty gallons suits a group better, spreads disputes over more floor, and gives you steadier water in a brackish setup where evaporation quietly concentrates the salt.
Why territories, not inches, set this tank size
A bumblebee goby defends the mouth of its cave with flared fins and short lunges, and a tank that is too small stacks those territories on top of each other. The loser of that arrangement has nowhere to retreat, stops competing for food, and fades while the bolder fish fatten. Floor area, sight breaks, and one more cave than you have gobies do more for peace than extra height ever will. Rearranging the bottom layout occasionally can reset a bullying problem in a small group, but in a genuinely undersized tank the same weakest fish keeps losing, which is the tank telling you it needs more ground.
The brackish question inside the size question
Most adult bumblebee gobies thrive in low-end brackish water, and the tank you choose must make holding that mix practical. In a ten-gallon, a missed top-up lets evaporation push salinity up noticeably between weekends, while a twenty-gallon forgives the same lapse with a smaller swing. Mixing replacement water to the same salinity before a change matters more than chasing an exact number daily, and a simple refractometer or hydrometer belongs with this species' kit. Some gobies are sold from fresh water and adjust gradually, so plan the transition over days, match the shop's water first, and never swing a small tank from fresh to brackish in a single change.
Feeding a bottom fish in a minimum tank
An adult bumblebee goby hunts small live and frozen foods near the bottom and often ignores dry food drifting above it, which shapes how a small tank must be run. Target feeding with a pipette or by placing food near each cave keeps shyer gobies fed without overloading ten gallons with uneaten frozen food. Their appetites are small but their waste from rich foods is not, so modest portions and prompt removal of leftovers protect water quality in the minimum footprint. If faster tankmates share the tank, feed the gobies after lights dim or use a feeding tube to the bottom, because a hungry goby in a big group is usually an outcompeted one, not a sick one.
Signs a goby tank has become too small
Signs a bumblebee goby tank is undersized include one fish permanently exiled to a filter corner, caves guarded so fiercely that tankmates cannot cross the sand, and bellies that stay hollow despite food going in. Salinity that reads differently at every test and water that clouds after each frozen feeding also point to a volume with no margin. Moving up in footprint, adding caves and plant cover, and trimming the group to what the floor supports are the structural answers. A goby that stops eating entirely, breathes rapidly, or shows damaged fins after fighting deserves prompt attention from a fish-savvy veterinarian alongside the layout fix.
Each goby's cave count, the brackish mix for change water, and the target-feeding routine are easy to garble when someone else maintains this tank. Keeping those specifics in KinsLe under Family Sharing means a family member mixing change water for the bumblebee gobies matches the salinity the fish already live in.