Gammarus, also known as Scuds, is a shrimp-like crustacean. It is an easy to culture live food that is an excellent size for many larger tropical fish. Even adult guppies can eat scuds. Cichlids and many killifish love them. This crustacean reaches about 1cm (0.4 in.). This shrimp-like, freshwater crustacean lives on decaying plants and detritus also eating algae and other microorganisms. It is gray to green in color. There are various species in North America, Europe and Asia.
This live food species is an excellent live food for most large tropical fish. It has the advantage of surviving aquarium conditions indefinitely so that it can be fed in abundance without fear of water fouling (do not, however, feed too many without adequate aeration since this organism will compete with fish for oxygen) .hTis species survives happily in aquarium quality water. It can tolerate temperatures as low as 0°C (32°F) and high as 35°C (95°F) but prefers temperatures ranging from 20-30°C (68-86°F). pH is not important. Culture containers (the author prefers 32 gallon plastic trash cans, preferably yellow or white colored) should be aerated and provided a good food source, such as plant cuttings or tree leaves.
Culturing scuds is simple in any container that can hold water. The author uses plastic garbage cans. Culture instructions follow:
1) Fill a plastic garbage can or an aquarium with aged water. Place about 5cm (2 inches) of dried leaves. Most tree leaves are good, but you should avoid oak leaves. Dried mulberry leaves are excellent. Place the container is a sunlit location. Aerate the water lightly. Scuds can survive winters outside in most of North America, but reproduce best at 20-30°C (68-86°F).
2) Add a starter culture of Gammarus; a few dozen will be enough.
3) Scuds feed on rotting leaves and microorganisms take grow on any surface. Provide adequate surface area to increase the population size by placing rolled up plastic screening in the culture container. The author uses plastic coated water cooling pads.
4) Within four weeks there will be enough scuds to harvest. Harvest by netting them with a fish net or by picking up the plastic screening or cooling pads and shaking over a bucket.
5) Feed the culture with additional leaves as they are consumed or decompose. Periodic, partial water changes are beneficial.
6) Cultures are long-lasting and sub-culturing is necessary only when production declines. Nevertheless, it is wise to maintain a replicate culture in case of a disaster (the author has lost outside cultures to neighbor’s herbicide poisoning).
Our starter culture is approximately 1000 Gammarus.