[2] A small fish, reaching a length of 10 centimetres (3.9 in) TL, it is purple with a diagonal black cap on its head.

The body colour varies from magenta to purple, and there is a jet-black diagonal cap running from the lip to the fore dorsal fin.

It is not advisable to house the blackcap gramma in an aquarium smaller than 30 gallons (115 litres).

Since it is commonly found in deep waters, it is best to avoid sharp aquarium lights.

The blackcap gramma can start acting territorially towards other fishes, including members of its own species, once it has settled in an aquarium.