gobies!

[hwchoy]

pure freshwater = water with no salt added whatsoever

[stormhawk]

Since they remain in the water column rather than stay at the bottom or sides of the tank, then I would think of them as a pelagic species. In this case I believe they shoal together in loose schools in the wild and feed on any passing food items that happen to be in the water column.

The best food that I could think of for them would be either live BBS, daphnia or just plain pre-soaked and crushed flake food.

Pure freshwater might not be to their liking but nonetheless, a basic measurement of the pH and hardness of their habitat should tell you how to handle them in captivity. I think with a little more diligence, most fishkeepers should be able to keep these species in a home aquarium.