Dear Blue Lobster:
I have one female blue crayfish living in a 15 gallon tank with a filter. Lately, the tank has been getting green on the inside walls and you cannot see the crayfish! I have to clean the tank out regularly, and every time it comes back. Am I doing something wrong? I at first thought I was overfeeding her, but I didn't feed her as often and it came back. If anybody can help, it would be appreciated.
Dear Gentle Sir:
It sounds to me like you have an algae problem! Though usually not serious, algae can effect water pH and oxygen levels. In the very least it's unsightly, like streaks in your toilet bowl during a family gathering. There are a few simple steps you can take to prevent this algae, none of which are very expensive.
Run your lights no more than eight hours a day. Any more than this and the algae will experience abnormal growth. Most crayfish habitat doesn't experience any more than eight hours of sun a day, so the cray won't be phased at all. Remember, like vampires, crayfish stalk for food at night under the cover of darkness and so prefer the dim shade that an unlit tank affords.
Get a scrubber. These simple tools are have a foam pad on the end, one side of which has a mildly abrasive surface. Going over the tank walls with a scrubber once a week is usually enough to maintain visibility and there's little to no disruption to the tank itself, especially when compared with introducing other animals into the aquarium. They usually sell for around a dollar.
Ghost Shrimp! These magical creatures, transparent save for their internal organs, sift through detritus and debris. Algae growth can be spurred by decaying foodstuffs so a fleet of Ghost Shrimp scanning the tank floor can prevent the cloudiness an algal bloom brings to the environment. At just 33¢ a piece you can not only clean up the tank for very cheap but also add some excitement with their gentle antics.
Good luck with your algal problems and just remember: Several cultures harvest kelp and algae to make flour and baked goods. Perhaps if you find it impossible to control the algal bloom you can do reap the benefits of a free food source! Your crayfish will not mind the intrusion, thinking it playtime with some five-legged water creature. Remember to tickle his or her belly; they love it and wriggle wildy in carefree abandon! Bon appétit and happy scrubbing!