©1997, 2001 Frank Ball
Color and size varies with species, diet, and age. Most are red, some are green, brown, tan, or blue with black or orange markings in various combinations. Often juveniles will be a light tan color that turns to a deep red as an adult. The coloration depends in part on their diet, and can change with a change in diet. Adult size is 2" to 6" for most US species. Some Australian varieties can be much larger.
They grow by molting, that is they shed their carapace (shell) when they outgrow it, and form a new hard shell. When they first molt they are soft, and very vulnerable to attack by other crayfish or fish. It can take a couple days for the new shell to fully harden. Juveniles can molt every week or so. Adults may only molt a couple times a year, and only under the right conditions. The empty shell should be left in the tank, where it will be consumed over the next few days to recover the lost minerals and help form the new shell.
Lifespan: about 2-3 years, but varies with species. Some live longer.
A temperature range of 65-77 F (18-25 C) is best for good growth of most species from the continental United States, but they can survive over a much wider range. Some species are tropical, some require cold water.
If the water is too soft or the pH is too low then there is a risk of calcium deficiency that could inhibit molting. Medium hard or hard water with a slightly alkaline pH, 7.5 - 8.5, is best.
They are normally 100% aquatic, but they can survive out of the water as long as their gills remain wet. They do not need to leave the water. The tank should be covered to prevent them from climbing out and going exploring around the house. They can climb up between the tank wall and a under-gravel lift tube, or climb up plants or a heater.
Since they like vegetables they will eat many plants. They will devour plants that nothing else will eat, like Java Moss. They will uproot the plants they don't eat. I have lots of floating Hornwort (Ceratophyllum demersum) in my tank. They don't eat that too fast (it grows fast), and they like the cover above them.
I now have a single crayfish in a 10 gallon tank with White Cloud Minnows, feeder guppies, and a Chinese Algae Eater. The crayfish ate some of the guppies but the survivors are keeping out of reach. She ate all of my Zebra Danios, and half of my White Clouds. The Chinese Algae Eater is much too fast for her, and it even hides with the crayfish and sucks on her back. I'd recommend feeder guppies, feeder goldfish, or minnows from a bait store (anything cheap).
In the past I kept a crayfish with common (feeder) goldfish, and the crayfish was not able to successfully compete for food against the goldfish. I had to "hand" feed it with a pair of tongs. One day I came home and the four goldfish (about 3" each without the tail) had eaten about half of the 4" crayfish, and they had it well cleaned up by the next morning. I've also seen small goldfish get caught and eaten within a few minutes. Do not keep a crayfish with a fancy goldfish or any fish that is slow moving or has long fins. Do not keep them with Weather Loaches (Dojos), as they will lay on the bottom of the tank and allow the crayfish to walk up and pinch them.
How to get a crayfish
Links with information on Crayfish
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