What zebra danios bring to a tank
A zebra danio is a small, striped, almost constantly moving fish that lives in the top layer of the tank and treats the whole water surface as a racetrack. It is one of the hardiest fish in the hobby, tolerates cooler water than most tropical species, and eats anything, instantly, the moment it lands. Those traits decide its compatibility: a zebra danio needs companions that are quick enough to get their share of food, robust enough not to be stressed by the constant motion around them, and shaped so that all that speed does not turn into nipping. In too small a group, or too short a tank, danios get bored, and bored danios investigate fins.
Tank mates that suit zebra danios
Fish with the same brisk outlook make the natural matches. White cloud mountain minnows share the danio's taste for cooler, well-oxygenated water and match its pace at the surface. Other danio species, including leopard and pearl danios, school and chase among zebras as equals. Cherry barbs and other smaller peaceful barbs hold their own at feeding time without returning any aggression. Corydoras cruise the bottom far below the danios' racing layer and are entirely ignored, and a bristlenose pleco is equally unbothered. Hillstream loaches appreciate the same strong flow, in a tank set up with current for both species.
Fish to keep away from zebra danios
Slow fish with long fins are the mismatch in both directions. A betta cannot escape the commotion, may be nipped for its trailing fins, and will starve politely while danios strip the surface clean in seconds. Angelfish and fancy guppies with flowing tails face the same nipping risk, and an adult angelfish may eventually eat a danio, settling the argument the other way. Shy, still-water species such as pearl gouramis find the relentless movement stressful. Very small fry and tiny shrimp are food to a danio, which hunts the surface with enthusiasm. Fish needing warm, still, soft water simply want a different tank from this cool-water sprinter.
Numbers and tank shape matter more than species lists
Most danio trouble is a numbers problem. Keep six at the very least and more if the tank allows, because a proper school spends its energy chasing and displaying to each other. Choose a long tank rather than a tall one: danios use horizontal swimming room, and a fish that can complete a full-speed run down the tank is far less likely to bother anyone. A tight lid is essential, since a fish that lives at the surface at speed will eventually find any gap. Feed a varied diet spread along the surface so the whole school, and everything beneath it, gets a share.
One feeding routine for a fast school
Danios are the fish most often overfed by one household member and fed again by another, because they always act ravenous. Keeping the tank's feeding details in KinsLe Family Sharing lets everyone see what the school has already had, so their tank mates get a fair share too.