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ive seen these guys everywhere. that are water cows? i cant find anything about them.

These guys are from the family Eleotridae. Often called sleeper gobies. There are marine, brackish, and freshwater species. The only freshwater species I ever found much info on was Eleotris picta. My lfs had in a freshwater sleeper goby but I never identified it perfectly. It was a mottled brown-black fish that sat on the bottom and ambushed small fish. I believe they get rather large.

Never heard them called "Water Cows" before ... ???

A small selection of species are featured in the venerable Innes book, including Dormitator maculatus (the Generic name Dormitator translates directly from the Latin as 'sleeper') which is a 10 inch long brackish water fish, Mogurnda mogurnda, an Australian species that stays small but which is a vicious fin-nipper comparable to Puffers, described by Innes thus:

As a community fish, it is one of the world's worst, being comparable in this respect to the much better known Gambusia affinis

and the predatory Oxyeleotris marmoratus, which is a carnivorous fish that WILL eat other fishes, and is equipped with truly cavernous mouthparts for the job of devouring other aquarium occupants up to half its own size, and therefore recommended only to be kept by the dedicated, and by people breeding fishes such as fancy Guppies in large numbers and thus needing a 'cannibal fish' to dispose of runts etc. Think of this latter species as being a sort of freshwater Stonefish, but minus the lethal venom, and you get the idea.

An odd Family of fishes, comprising some pretty species, but not a Family to be taken on lightly, as some of them are candidates for species aquaria, others are brackish fishes requiring up to 25% marine strength salt water, and others boast some peculiar requirements.

Sham, your mottled brown fish sounds a LOT like Oxyeleotris marmoratus. See if this photo looks like your 'unidentified' fish. If it was a ravenous carnivore, then it was likely to be this one.


Panda Catfish fan and keeper/breeder since Christmas 2002

A close match but the black seems more defined on that one and the shape from that angle doesn't look quite as wide and flat. I don't know how much variation in color there is and I mostly saw this guy from the top. He spent 99% of his time sitting on the bottom trying to blend in. When he did move though it was quite impressive. He'd pop up with so much force the gravel and his tail would smash into the sides of the tank sounding like he was about to crash thru it. Then he'd sink back down to the bottom and when the detritus and gravel settled again there was 1 less goldfish in the tank.

All the "Water Cows" I've seen are Eleotris fusca. I made a profile on the fish here. There used to be a picture, but at some point in time it disappeared.

Anyway, contrary to the name they are given by stores, they are actually highly predatory.

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I'm not your neighbor, you Bakersfield trash.

Oh, an update.

The old Innes book claims that Oxyeleotris marmorata (which is its correct valid name according to Fishbase, not Oxyeleotris marmoratus) reaches 6 inches or 15 cm. However, Fishbase cites na adult maximum SL of - wait for it - 65 cm for this fish, and cites that it is the largest of all the Sleeper Gobies, with an appetite to match. Indeed, this size may make it the largest of ALL Goboioid fishes ...

Even at small sizes it's a fearsome predator. At full adult size, it's the Goby version of the Great White Shark. You wouldn't even be able to keep it with Jaguar Cichlids because it would eat the Jags ...


Panda Catfish fan and keeper/breeder since Christmas 2002