The minimum for an adult tiger barb
An adult tiger barb needs at least thirty gallons, and the fish's group behaviour is the reason the number sits that high. A single adult reaches about three inches, deep-bodied and striped, but tiger barbs are never single fish in practice. They run in a scrum of constant chasing, sparring, and short races, and that scrum needs a tank long enough for a chased fish to actually get away. Thirty gallons gives a group of eight to ten the volume and the swimming length to burn energy on each other in rotation, which is precisely what keeps their reputation for nipping from becoming your other fishes' problem.
Why group size and tank size rise together
A tiger barb in a pair or trio concentrates its mischief, while a tiger barb in a proper group dilutes it. With eight or more in thirty gallons, the dominant fish cannot single out one victim, the hierarchy reshuffles harmlessly through the day, and long-finned tankmates stand a fair chance because the barbs are busy among themselves. Shrink the tank and the group together, as beginners often do, and every chase ends at glass with the same loser cornered. If you want fewer fish, choose a different species; the honest minimum for this one is a crowd in a tank that lets the crowd move, and that pairing is not negotiable husbandry.
Setting up thirty gallons for constant motion
Setting up a tiger barb's minimum tank means an open mid-water racing lane, planting and wood at the back and ends for the fish that needs a breather, and a lid, because a startled barb is perfectly capable of leaving the water. Strong filtration that keeps up with a dozen active, eagerly fed fish matters more than elaborate decor, and moderate flow along the tank gives the group something to swim against. Avoid delicate, slow, long-finned companions in this footprint no matter how peaceful the barbs seem at the shop, since a minimum tank leaves slow fish nowhere to retire from attention.
Feeding and water in an active barb tank
Adult tiger barbs eat like they swim, fast and competitively, and a thirty-gallon group turns food into waste at a pace that punishes lazy maintenance. Spread meals across the water so the boldest fish cannot monopolise one corner, feed amounts the group finishes quickly, and keep weekly changes generous because the tank's stocking is athletic rather than ornamental. Stable warmth and clean, well-oxygenated water keep colours strong, with the males' orange noses deepening when the group is settled. In the minimum volume there is little slack for a missed week, so the routine should be written down and shared with whoever else feeds them, not carried in one person's head.
Signs a tiger barb tank is undersized
An undersized tiger barb tank announces itself through torn fins, one barb perpetually hiding behind the filter, and tankmates that only feed after dark. Constant sparring that draws blood, fish pressed at the surface, and water that clouds after every meal all say the group has outgrown the footprint or the filtration. Adding length, lifting the group size if it has thinned, or removing the victims to calmer water are the real remedies, in that order of thinking. Barbs that stop eating, show rapid breathing across the whole group, or develop widespread marks after fighting need a prompt water test and a fish veterinarian's advice rather than a wait-and-see week.
The group count, the no-long-finned-tankmates rule, and the feeding spread for tiger barbs are facts a substitute feeder can easily get wrong in good faith. Keeping them in KinsLe through Family Sharing shows anyone helping with this tank why the barbs live in a crowd and how their meals are handled.