Troubleshooting community setups: see the compatibility result using temperature, pH, GH/KH, adult size, behavior, schooling needs, and predator/prey rules.
Short answer: Likely, when tank size, group needs, and water parameters are handled. Plan for at least 20 gallons before adjusting for group size, filtration, and aquascape layout.
Data confidence: high
Verified sources: GloFish care guidance | SeriouslyFish Danio rerio
glofish danio | harlequin rasbora | glofish danio | harlequin rasbora
This verdict assumes normal social groups, not one stressed specimen. GloFish Danio should be planned at 6+; Harlequin Rasbora should be planned at 6+ before judging long-term compatibility.
A compatibility score checks adult size, temperature, pH, hardness, temperament, and tank volume. Real tanks add variables the score cannot see directly: feeding aggression, cave ownership, plant cover, and whether fish can constantly see each other.
GloFish Danio and Harlequin Rasbora may compete for the same swimming lane, food path, or line-of-sight territory. Start with at least 20 gallons, then use hardscape, tall plants, and separated feeding zones to reduce chasing before it becomes a pattern.
Confidence: high. Aggression, predator/prey, shrimp risk, schooling, and tank size rules are evaluated from curated freshwater attributes.
Problems can happen even when the gallon number is technically adequate. Check feeding order, repeated access to the same cave or plant mass, school size, and whether the aquascape gives either fish a direct line of sight across the whole tank.
Use tall plants, rock piles, driftwood, and separate feeding stations so a dominant fish cannot patrol one open lane from end to end.