The beautiful blue eyed rainbowfish of the genus Pseudomugil have quickly become favourites among nanotank enthusiasts and planted aquarium lovers alike. These small rainbowfish reach sized of only about 2", and do quite well in small aquariums, and especially well in planted tanks. Gertrude's Rainbowfish is an active, shoaling species, that should be kept in groups of 6-12 fish, at a minimum. Male Gertrudae are more colourful than females, and in the presence of females, will often spare with one another, which involves flashing their fins and enhancing their colouration. These fights do not result in damage to either fish.
Care should be taken when choosing tank mates for these fish, as they are quite small. Larger fish may eat them, or outcompete Gertrude's Rainbowfish for food. The various species of Pseudomugil should not be mixed, as hybrids may occur. Small, placid tetra, dimunitive catfishes, and invertebrates all make great additions to an aquarium with these fish.