Halocaridina rubra: The Hawaiian red volcano shrimp

by Robert Paul Hudson

If you go into a pet store on the Hawaiian Islands, you may find tiny bright red shrimp being sold as feeder shrimp.  Many hobbyists are discovering that these little feeder shrimp are fascinating to observe in their own aquarium.

Red volcano shrimp are endemic to a unique environment on the Hawaiian Islands called anchialine pools. These are still water pools in larva rock craters near the coast, but disconnected from the sea and fed by the subterranean water table within the lava rock base. These pools contain no vegetation other than algae and no fish. The water is affected by tides and ranges in salinity from less than 2% to over 33% .

These shrimp are tiny- usually no more than half an inch in length, which makes them difficult to keep with any fish without being eaten. They are highly adaptable to water conditions, and while most people keep them in brackish water, they will adapt to pure freshwater with moderate to high alkalinity.  Plants would not be part of their natural environment.

Diet

The shrimp commonly graze on algae and cyanobacteria that forms a crust on the lava rock but are also equipped to filter feed by fanning the water into their mouth to catch floating particulates, and they have been observed feeding on insect carrion. In the aquarium they will take flake food and algae wafers and even freeze dried fish food.  Feeding antics are quite entertaining to watch. When food falls to the bottom and startles the shrimp, they immediately swim up to the water surface and then back to the bottom, and sets off a chain reaction with any other shrimp in close proximity.

Reproduction

In the anchialine pools Halocaridina spend part of their time in deep, dark, subterranean crevices, and in shallow brightly lit areas exposed to the water surface. Spawning occurs in the subterranean areas. The hatched larva swim up toward the light which triggers the four stage larva development.  These shrimp will readily reproduce in the aquarium and the larva will feed on liquid fry food.

Aquarium set up

A ten or twenty gallon aquarium is a good size aquarium for a nice size colony of these little red gems. Stack lava rock along the back of the aquarium to provide plenty of hiding places, places to spawn and explore. I use crushed coral gravel as a substrate, but crushed lava rock would be another alternative. For a brackish environment, keep the salinity around 12 ppt (about 1.008 sg) to 23 ppt (about 1.016 sg).

A simple sponge filter is really all that is needed, but if you are using any type of outside filter be sure to use a sponge pre filter over the intake tube of the filter to prevent the shrimp and larva from being sucked up. Water circulation should be slow and these shrimp can withstand long periods without water changes.

Lifespan

These unique shrimp have been dubbed “super shrimp” for being highly adaptive and for having one of the longest life spans of any shrimp specie- up to twenty years!  Keeping these creatures healthy and happy should be easy and the reward is hours of entertainment for many years.