Small does not mean solitary
Zebra danios are small but active and social. Our planner calls for a group of six in a 20-gallon long tank or larger. Bettas have a different social pattern: keep one and treat community housing as a separate decision.
Match the whole environment
Compare temperature, pH, hardness, swimming space, and feeding behavior. Guppies and platies favor harder water. A shared temperature range is only one part of compatibility.
Plan for breeding and behavior
Livebearer numbers can grow quickly. Account for offspring and sex ratios, and have a plan for fish that cannot remain together. Peaceful is a general tendency, not a promise about every individual.