Saw Anableps sp. aka Four-eyed fish for sale at the Geylang branch of Seven Star Aquarium. A small group might make a very interesting addition to a brackish water paludarium, although it's capable of growing up to 20 cm or more in length. Quite odd that they were all huddling at the bottom though, since they're supposed to be cruising around just beneath the surface.

Not sure if there's more than one species available in the trade, but my assumption is that this is Anableps anableps:

http://www.seriouslyfish.com/species/anableps-anableps/