There are several intriguing species of Roundheads (Plesiopidae) which are both interesting and easy to keep. 

In the wild, most species will stay hidden and hunt at night, they mimic this behaviour in the aquarium so they are not often seen during daylight hours, although they will appear more in time.

These fish are generally quite hardy if given a varied diet.
They are not well suited to tanks with fast or aggressive fish, as they might hide and therefore not get sufficient food.
One should avoid keeping them with Hawkfish, Triggerfish and aggressive Wrasses for example. 

Below are short descriptions of the species most suited to aquaria.

Assessors
Pretty, small fish that somewhat resemble Grammas and Dottybacks.
They are hardy, max. 2.5 inches (6 cm) and reasonably peaceful. Suitable for both coral and nano aquariums. 

Calloplesiops
A unique fish which is hardy when fed correctly, but does require extra attention when adjusting to life in captivity. They will not thrive when kept together with aggressive species. 

Plesiops
These fish are very aggressive and not often seen in aquaria.
Most species do not get very big and can therefore be kept in smaller tanks.

Calloplesiops

Calloplesiops altivelis is the only species of the Calloplesiops genus. 

There was thought to be another species, Calloplesiops argus, as the fish develops spots as an adult. 

These spots on the fins merge into each other when the fish is fully grown.

These fish mimic Morays (Gymnothorax meleagris) when feeling threatened, by swimming into a hole and sticking their tail out. 

Just a moment...
Just a moment...