Hypoplectrus guttavarius

Hypoplectrus (Hamlets) are a colourful and relatively small predatory fish which are well suited to tank life.
All the species are very alike, when not taking colour and habitat into account. 

They will eat small fish and crustaceans which can be swallowed, but are otherwise not a threat to the other animals in the aquarium. 

Hamlets are fairly hardy and easy fish, but are not very good at adjusting to tank life. They should therefore be bought as young as feasable, and should be moved around as little as possible.
They are easy to feed and do not require live food, so a varied diet of frozen fish, crustaceans and the like is sufficient.
Needs to be fed once a day.

The Sea Bass family (Serranidae) spans a broad spectrum with regards to how suitable they are to aquaria, as some are best suited to specialist or larger aquaria, while other are often seen in reef aquaria.

Below are described the five subfamilies one sees most often in aquaria. There are however other species one can also keep under the right circumstances, but these are for the most, large predatory fish.

Anthias (Anthiinae)
The Anthias species spans over many different genera, but the most common is the Pseudanthias genus. They mostly have an attractive orange or pink shade.

They are generally all reef safe and peaceful.
There is however a large difference to their food requirements, some species demand constant feeding, whereas others can get used to being fed once a day.

The easiest species are the following: P. bartelettorum, Anthias, Luzonichthys, Nemanthias, Odontanthias, Pseudanthias, Sacura and Serranocirrhitus

Liopropomatinae
This subfamily encompasses some of the smallest fish in the Serranidae family, they can be very colourful but shy. The Liopropoma genus encompasses many species which are suitable for aquaria, however they normally thrive best in a very peaceful- or nano aquarium.

Grouper (Epinephelinae)
These fish grow typically too large for most home aquaria. There are however some species that do lend themselves to the slightly bigger domestic aquarium. Several of the species look very impressive and often have a interesting personality, and they often recognize the aquarist and will become tame over time. 

Groupers are predatory fish and eat everything they can swallow; fish, crabs, shrimps and sometimes other invertebrates. Like most large predatory fish they excrete a lot of nutrients to the water, so one therefore needs a good filter system.

Groupers include among others the following genera: Aethaloperca, Cephalopholis, Chromileptes, Epinephelus, Paranthias and Pogonoperca

Soapfishes (Grammistinae)
These fish are like the Groupers predatory fish, but they do not typically, grow so large. They are relatively hardy, but some of the species demand a thorough preperation if one wants to be successful.

Soapfishes are generally very shy and will often hide under an overhang during the day, and hunt at night.

Soapfishes include among others the genera: Grammistes

Serraninae
The most common genera in captivity is Dwarf Seabasses (Serranus) and Hamlets (Hypoplectrus).

See the description of the individual genera below.

About references

Scott W. Michael. 2001. Reef Fishes volume 1 - TFH Publications / Microcosm Ltd. - (English)

Bob Fenner. The Basses, Family Serranidae - Wet Web Media - (English)