Cutting the top off a 1L plastic bottle, Justin pierces the bottom with a thingamajig, and inserts some rigid tubing with an adjustable plastic valve you turn to an appropriate drip rate. It is used to drip aquarium water into the bag-o-fish while it's floating in the tank. It's a slower but milder method to equilibrate his water with yours. Drip rate depends on how sensitive a species might be to changes in pH, for instance, or how different your water parameters are to his. It's easier on the fish/shrimp.
He does it for no charge, at least for me he didn't charge. Shows how much he still loves the hobby and appreciates his customers. Try to get this kind of service and commitment from any other LFS.
Sometimes it's in our best interest to not always shop for the cheapest prices, but to keep places like these in business. Overhead in SFO is not cheap.