Crustaceans (Phylum Crustacea)

There are more than 38,000 species of crustaceans known worldwide (Ruppert and Barnes, 1994), so the job of identifying hitchhiker crustaceans is not going to be easy. In most cases identification to family level is about as far as you can get. Jones and Morgan (2001) A Field Guide to Crustaceans of Australian Waters should prove helpful as well as Jim Lowry's crustacea.net. Both these resources can guide you to the higher level taxa.

Class Maxillopoda

Barnacles (Subclass Cirripedia)

There are some 900 species of barnacles worldwide (Ruppert and Barnes, 1994). Barnacles are all sessile and most feed on plankton which they capture with their cirri - feather like oral appendages. Survival in the aquarium is not guaranteed, but a tank with a deep sand bed may be able to produce enough plankton to support some barnacles.

Barnacle (180G)

Copepods (Subclass Copepoda)

There are over 7,500 species of copepods described (Ruppert and Barnes, 1994). Most are marine and there are a large number of freshwater and some terrestrial species. Planktonic copepods are mainly filter feeders and phytoplankton is the principle part of their diet. Most other copepods feed on algae, bacteria or detritus. There are some parasitic species of copepods.

Copepods on glass (60G)

Class Malacostraca

Subclass Hoplocarida

Mantis Shrimps (Order Stomatopoda)

The mantis shrimp are much maligned in the marine aquarium hobby and while some species may prey on tank inhabitants, most will do fine, especially if fed regularly. I have a number in my tanks and to date they have not caused any problems at all.

There are around 300 species of mantis shrimps (Ruppert and Barnes, 1994) and they are probably the most intelligent crustaceans. Some are very beautiful. See The Lurker's Guide to Stomatopods for more information on mantis shrimps.

Mantis Shrimp Haptosquilla trispinosa (40G)

Mantis Shrimp Haptosquilla trispinosa (60G)

Subclass Eumalacostraca

Tanaids (Order Tanaidacea)

Tanaids are a small peracaridans live in the sand in burrows. They eat mainly detritus. There are a few in 60G FOWLR, but 50G Reef 2 has hundreds, maybe even thousands.

Tanaid in burrow in sand (60G)

Tanaid in burrow in sand (50G2)

Tanaid after removal from tank for closer inspection (50G2)

Amphipods (Order Amphipoda)

There are some 4,600 species of amphipods. Most are marine, but there are many freshwater species and some semi-terrestrial and terrestrial species. The familiar leaf hoppers are an amphipod. Most amphipods are detritus feeders or scavengers. There are some predatory species and even some parasites, including whale lice.

Amphipods (50G1)

Amphipod (4mm) in burrow in sand (60G)

Two amphipods in the same burrow. The larger one appears to have eggs. (60G)

Isopods (Order Isopoda)

About 4000 species of isopods have been described. Most of these are marine, but there are a number of freshwater and terrestrial species including the familiar slaters (wood lice). The majority are scavengers and omnivorous, but some are mostly herbivorous. A number of fish parasites are isopods, including the familiar fish lice.

Isopod (4mm). Dorsal view on right and ventral view on left. This isopod appears to be a herbivore, eating algae on the glass. (60G)

Isopod (5mm). The dorsal and ventral view of one of 5 isopods removed from the sump and transferred to another tank. These all appear to be the same species. (60G)

Isopod (5mm). This appears to be the same as the ones on the glass. (60G)

Decapods (Order Decapoda)

The decapods are the familiar true shrimps, crayfish, lobsters and crabs. These are mostly marine, but there are a number of freshwater shrimp, crayfish and crabs and a few amphibious and terrestrial crabs.