Blue Opaline Gourami

(Trichogaster trichopterus) 

Opaline Gouramis are a domesticated strain of Blue gourami and are a familiar sight in community set ups. Males are inclined to be rather competitive with one another and show the marbled pattern seen in other forms when at their most assertive. These fish have long been used as a larger accent fish amongst smaller shoaling species and the key to successful cohabitation is to keep them occupied. Although gouramis are often sold as pairs, these are not monogamous fish and males will court females in the knowledge that they'd leave his territory if they weren't interested. In the confines of an aquarium this is not an option, so add multiple females to spread the male's attention. The sexes can be easily distinguished by the shape of their dorsal fin - small and rounded in females, long and pointed in males. As this fish comes in many colour forms such as Blue, Opaline, Three-spot, Gold and White (a very pale strain of gold) these can all be mixed if you so desire. To allow them to avoid one another on occasion, the aquarium should be over 90cm/36" in length, with a good amount of aquatic planting to provide shelter and break the sightlines. Like most gouramis, the hair-like pelvic fins are equipped with taste buds and are used extensively to investigate their environment and one another. 

https://www.fishkeeper.co.uk/fish/freshwater/anabantids/opaline-gourami-