The short answer: small, rigid, and full of home water
A small rigid container with a screw or clip lid, filled well up with its own tank water, suits a bumblebee goby best for a short trip to a specialist. A bumblebee goby is barely the length of a thumb joint, lives on the bottom, and in most home setups keeps to brackish water it is precisely adapted to. A fish bag is a poor match for it: bags slosh hard for a bottom fish, offer nothing to shelter beside, and their thin water layer changes temperature in minutes. A little food-grade tub or specimen pot holds temperature steadier, cannot be punctured, and lets the goby sit on a solid floor the way it does at home.
One goby per pot, plus its territory
Carrying bumblebee gobies separately is the safer default for a specialist trip. These are territorial fish that stake out a shell or tube each and bicker over it, and a shared container on a stressful morning concentrates that squabbling into a space with no escape routes. Include the goby's own small shell, cave, or tube section in its pot, because a bumblebee that can back into its territory copes with travel remarkably calmly. Size the container so the shelter fits with room to spare and the lid still closes without squeezing. If your group genuinely lives peaceably and the specialist wants to see them together, that is a decision to confirm when booking, not at the tank glass.
Why the water matters more than the box
Water taken from the goby's own tank is the single most important part of this container choice. Bumblebee gobies kept in brackish conditions react poorly to abrupt moves between fresh and brackish water, and a container casually filled from a tap undoes months of careful keeping in one morning. Fill the pot high enough that the water does not slop violently with every turn, leaving only a small air space under the lid. Catch the goby by herding it, shelter and all if possible, or with a small cup, never by chasing it with a net across open tank, since these fish are quick, bottom-hugging, and easily exhausted before the trip begins.
The drive and the wait
A dark, level resting place in the car is what a travelling bumblebee goby needs. Set the pot inside a small insulated box or wrap it in a towel so light and temperature both stay steady, and wedge it where it cannot tip, because a tipped screw-lid pot in a footwell is a disaster a bag would have survived. On arrival, keep the container closed and shaded in the waiting area, and tell the specialist the water in the pot is the fish's home brackish water, so nobody helpfully tops it up or transfers the goby into fresh water while it waits. Short trips need no food, and feeding only clouds a tiny volume.
Home again and what to report
Acclimate a returning bumblebee goby by standing its pot where temperatures can equalise, then mixing small amounts of tank water in before tipping it gently back beside its territory. It may sulk in its shell for hours after a trip, which is normal for this species, but it should take small live or frozen foods again by the next day. Report a goby that refuses food for several days, fades in colour, or sits in the open breathing hard to the specialist who examined it. Recording the goby's water type, salinity routine, shelter habits, and favourite foods in a KinsLe Pet Passport gives the specialist the facts that decide its care before the lid ever comes off.