Maintaining a freshwater aquarium isn't as simple as selecting a combination of your favorite attractive species of fish. Apart from care requirements, many species don't get along with other species, and therefore are hazardous together. Some fish species even have major problems with themselves. Plecos (Hypostomus plecostomus), for one, should never live together, with one exception.
"No" to Multiple Plecos Together
When plecos -- an abbreviation for plecostomus -- are in community aquariums, they can indeed thrive, but only if they are the sole representatives of their species. They often do wonderfully alongside other types of community freshwater fish. When plecos reach maturity, they simply cannot get along with fellow plecos. They can be highly territorial around each other. Therefore, it can be extremely dangerous ever to house them together. When they're alone and away from other plecos, they can make serene and pleasant community tank inhabitants, however.
Although multiple plecos are generally an emphatic "no-no," one exception exists. A pair of plecos can sometimes flourish together, but only if they were introduced to a tank at the same time, and as babies. If two plecos are used to being around each other and haven't ever been apart, they can often find success -- and tranquility -- in being around each other.
Suitable Possible Tank Mates
Solo plecos usually are mild-mannered in community tanks. Some of the various freshwater fish that can usually live happily alongside plecos include many rasboras, danios and tetras. If you're ever uncertain about housing certain types of fish together, whether plecos are involved or not, don't hesitate to consult with an aquatic veterinarian beforehand. Always keep your focus on the safety of all community tank residents.
Housing Plecos the Right Way
Keeping multiple plecos, in most cases, is a recipe for their unhappiness. Since happiness if your goal, keep your pleco content and in strong health by housing him in a tank that can hold no fewer than 75 gallons of water. Ample room is a must for them, as they are pretty big when mature. Adult plecos sometimes grow to as big as 18 inches. Thick plants make good additions to their aquariums, especially ones that have wide leaves. They also appreciate ample large places to hide, such as caves, driftwood and stones. As they have voracious appetites and therefore expel lots of waste, they always need to live in aquariums with good filtration.