The Sifter Gobies
When it comes to gobies, the sifters (also commonly called sleepers for some reason) can get relatively large, with some species reaching 6 or 7 inches in length. They’re generally quite peaceful with other sorts of fishes though, so don’t be worried about their size. They’re also a hardy bunch and can be quite useful at times, too.
They feed on tiny sand-dwelling invertebrates, and collect them by scooping up mouthfuls of sand, which is also why they’re often called sifters. They’ll essentially make a shallow nose dive into sandy substrates, fill their mouth with sand, and then quickly sift through it in order to capture any edible organisms within it. The sorted sand is ejected through the gill slits behind the head, and then they’ll take another scoop.
This feeding activity can help to keep the upper layer of a sand bed cleaner, but you should note that if you’re trying to maintain a thriving deep sand bed, these fishes will indeed eat some of the beneficial organisms living in it. I’ve found that they don’t really deplete a sand bed of critters if kept in a large enough system housing enough sand, but they can literally clean out a relatively shallow sand bed in a smaller aquarium.
Again, they usually get along fine with other types of fishes, but they may not get along so well with other species of sifters or other individuals of the same species, either. So, it’s best to keep just one in a tank, or a mated pair, unless the tank is large and has plenty of room for everyone. They’ll typically learn to take a variety of fish foods too, although some hobbyists have reported otherwise on occasion. I’ve had no problems keeping the two most common species Valenciennea puellaris and V. strigata, but can’t say much for the others.