Water Cow Goby: Care, Tank Size, Max Size & Tank Mates

Scientific NameEleotris Picta
Common NameWater Cow Goby, Sleeper Goby
Temperature73-82°F (23-28°C)
Water pH7.4-8.2
Max Size10-24 inches

Water Cow Goby Facts:

  • Water Cow Goby are larger fish that require a minimum of 100 gallon tank for just one fish.
  • Water Cow Goby are placed into a category called ‘monster fish’.
  • Water Cow Goby are often referred to as ‘gentle giants’, this is due to their lazy hunting style, not because they are particularly good with other fish.
  • Water Cow Goby are all wild-caught from Ecuador, and reports of the lengths they can grow up to, and the average lifespan of these fish, varies greatly.
  • Water Cow Goby can be mistaken for other species of Goby, so it is important to make sure they have been identified correctly before purchasing one online.
  • There is not much information online about Water Cow Gobies, and new information about them is being discovered all the time.

Water Cow Goby Care

Water Cow Gobies are one of the larger fish to keep in the fishkeeping hobby. They require a large tank, but they are an interesting fish to keep. They aren’t particularly colorful, but they have a mix of browns and tans on their bodies. These colors are beneficial in the wild so that they can hunt smaller fish. This camouflage in addition to its slow moving nature helps it to be an efficient hunter. Water Cow Gobies have been known to have a greyish color to their bodies as well. Water Cow Gobies’ coloration will change from lighter to darker, seemingly with their mood, but this is more likely just for camouflage purposes so that they can be effective hunters.  With several types of Gobies for sale online, it can be difficult to find a seller who is selling a true Water Cow Goby, and not another species of Goby just mislabelled.

Water Cow Gobies have sexual dimorphism. This means that the female and male are different, but their differences can be difficult to spot until they have grown into maturity. The male Water Cow Goby has a longer anal fin than the female.

When it comes to shape, the Water Cow Goby has a torpedo shaped body, and it has a shorter fin than you would expect for a fish this size. Water Cow Goby owners describe these fish as having an interesting personality and swimming pattern.

Water Cow Goby
Water Cow Goby. Photo by David J. Stang, CC BY-SA 4.0, via Wikimedia Commons

Water Cow Goby Tank Size

Water Cow Goby are larger fish, so they will require a tank that is at minimum 100 gallons. You want to add additional gallons for additional Water Cow Goby. Water Cow Gobies can be typically found in the wild inhabiting rivers with varying currents, freshwater and slightly brackish waters at river mouths. In their natural habitat they typically reside at the bottom, so they would benefit from a tank that is wider opposed to a tank that is tall. This will give them more room to roam. You will also want to make sure that you have a good lid on your aquarium as Water Cow Gobies have been known to jump out of their tanks.

Water Cow Gobies will also benefit from a setup that contains a soft, deep substrate that they will slightly bury themselves in while they hunt for their food. You will want to offer a sandy or fine gravel substrate. Water Cow Gobies also like plenty of places to hide. They will perch themselves on rocks, or under driftwood while they wait for smaller fish to pass by to eat.

Water Cow Gobies fare best when they are kept at a temperature of around 73F to 82F, and a pH of 7.4 to 8.2.

Feeding & Diet

Water Cow Gobies are carnivorous fish that spend most of their time at the bottom hunting for smaller fish to eat. In their aquarium, you will notice them spending most of their time hunting along the bottom of their tank. Water Cow Gobies like to find places to hide and lay in wait for smaller fish to swim by them. Water Cow Gobies coloring, and still nature offers it the ability to be able to hunt in the wild without doing much at all which gives them the appearance of being a gentle and non aggressive fish. Water Cow Goby are often called ‘gentle giants’, this is not because they are particularly good with other types of fish, they are called this more due to their lazy nature when hunting.

In captivity, Water Cow Goby needs to be fed a diet of high quality proteins. They can be fed live foods, or frozen foods. Over time you can condition your Water Cow Goby to accept flake or pellet foods, but this will not be a complete diet for them. They can be fed bloodworms, earthworms, live fish, and shrimp. If you are feeding them live foods, they should be given these infrequently. They should be fed once a day, and Water Cow Gobies will overeat, so take care that you are feeding your Water Cow Goby on a schedule.

Water Cow Goby Max Size & Lifespan

There are many reports of Water Cow Gobies growing many different lengths at full maturity, you can expect your Water Cow Goby to grow anywhere from 10 inches in length all the way up to 24 inches. They are typically sold around 12 inches in length online, but you can find them for purchase larger and smaller. Water Cow Goby can live anywhere from 8 years to 20 if they are properly cared for. The key to keeping your Water Cow Goby happy and healthy is setting it up in a tank that is as close to their natural environment as possible, and feeding them a high quality protein diet.

Tank Mates for Water Cow Gobies

Water Cow Goby are large carnivorous fish, and this could make it difficult to find tank mates as they will eat any fish that is smaller than they are without discrimination. This means that they will even eat other Water Cow Gobies. If you are planning on housing more than one fish in a tank that contains a Water Cow Goby, you will want to make sure that you have a tank that is big enough to house them comfortably, and give them plenty of places to hide from one another. Since Water Cow Goby are bottom-dwelling fish, choosing other fish that inhabit other parts of the aquarium is a good idea as well if you are planning on placing these fish in a community setup. They do best in a single species setup, or paired with other fish that are roughly the same size as they are and have the same temperament.

Even though Water Cow Gobies are often called gentle or lazy fish, this doesn’t mean that they will not eat other fish in your aquarium, this just means that they do not seem to stress easily when disturbed by other fish. Water Cow Goby can even be aggressive and territorial of other Water Cow Gobies.

If you have a tank large enough to house other fish with your Water Cow Goby, another fish from the monster fish category could be an ideal tankmate. Perch, Gouramis, and other Gobies could all be potential tank mates as long as you keep in mind that they need to be roughly the same size. 

Are Water Cow Gobies Aggressive?

Water Cow Gobies are a large but docile species of fish. They are a great non-threatening addition to any large aquarium set up as long as you keep in mind that they are carnivorous and will eat any fish that are smaller than the size of their mouth. The key to success in placing these fish in a community tank, you will want to make sure the tank is large enough, and there are no fish smaller than your Water Cow Goby. They are non aggressive to people. Some owners of Water Cow Gobies have reported that over time they recognise their owners, and can be taught to take food from their hands.

Breeding and Price

Since Water Cow Gobies are caught in the wild, and not bred in captivity, the pricing for them varies greatly online. Water Cow Gobies are larger fish, and breeding them in captivity could possibly be problematic due to their aggressive nature during spawning time and territorial aggressions with other fish of their same species.

If you are looking to purchase a Water Cow Goby for yourself, you will expect to spend anywhere from 40 dollars to over 100 dollars. They will not be readily available for purchase in pet stores, but they are somewhat easily found online. It is possible that a specialty pet store could have them, but you will be more likely to purchase one online. If you are purchasing online, make sure that you go with a reputable seller. There are many species of Goby fish, and they are often misidentified for one another by online sellers.