The tiger barb is a bold, black-striped Sumatran schooling fish whose bad reputation is earned almost entirely in tanks that are too small with groups that are too few. Adults reach two and a half to three inches, swim hard all day, and run a busy social hierarchy. The working setup is a 30-gallon tank - long rather than tall - holding a school of at least eight, and ten to twelve is better. In that configuration tiger barbs are hardy, funny, and mostly harmless; in a 10-gallon trio they are a cautionary tale. It is a beginner-priced fish that is not a beginner setup.
The group is the whole strategy
Tiger barb society is a ladder, and the school spends its day maintaining it - chases, displays, mock fights, all inside the family. With eight or more fish, that attention is spread so widely that no individual, barb or tank mate, gets much of it. Drop to four and the ladder collapses onto the weakest barb, then onto everything else in the tank. This is the rare case where adding fish reduces aggression, so buy the full school at once and top it up promptly after losses. A big school is also simply the best version of this fish to watch. Once a week, watch the school at feeding from across the room; a healthy hierarchy is loud, fast, and quickly settled.
A tank built for chasing
Give tiger barbs length to chase in, sturdy plants and wood at the back for the losers of chases to duck behind, and an open middle lane. They are warm-water fish, comfortable in the mid-to-upper 70s Fahrenheit, unfussy about chemistry within the normal community range, and hard on delicate plants only mildly - robust species hold up fine. Filtration should match a well-fed, active school, and a lid matters, because feeding time turns the whole group airborne. Regular water changes keep the black stripes black and the orange fins lit; neglected tiger barbs fade to grey like any other fish.
Tank mates: robust or nothing
The tiger barb rule never changes: no long fins, no slow swimmers, no exceptions for that one peaceful-looking betta. Angelfish, gouramis, fancy guppies, and bettas will be harassed in a tiger barb tank no matter how large the school is - the school's manners end at its own species. Good companions are fish built like the barbs themselves: other robust barbs, fast danios, loaches that hold the bottom, and larger tetras with short fins and quick turns. Rainbowfish of similar size also thrive in the current of a busy barb tank. Kept in that company, a tiger barb school is the engine of a lively tank rather than its problem.
House rules everyone can see
A tiger barb tank fails by addition more than by neglect - a new housemate or a kind-hearted gift fish with flowing fins undoes the whole balance overnight. Write the rules down where anyone tempted to add a fish will see them. KinsLe's Family Sharing keeps this tank's profile and its no-long-fins rule in front of the whole household, so the school's peace is protected by information instead of by one person's memory.