Electric Blue Crayfish

The Midnight Slaughter (Fish Fatalities):

The Sleep Assassin. During the day, they look clumsy and slow, fooling beginners into thinking their fish are safe. THE LETHAL ERROR: When the lights go out, fish fall asleep and sink to the bottom (especially Corydoras, Plecos, and long-finned Bettas). The Crayfish uses the dark to sneak up on them, reach out with its massive claws, and violently snip them in half or rip their tails off. They CANNOT be kept in a community tank. They must be kept strictly alone or only with ultra-fast, top-dwelling fish (like Zebra Danios) that never sleep near the bottom.

The Plant Chainsaw (Aquascape Destruction):

The Deforestation Error. Never put them in a beautiful planted aquarium. Crayfish are both gluttonous omnivores and neurotic interior designers. They will literally use their claws like hedge-clippers to aggressively cut the stems of all your expensive plants right at the base, leaving them floating ruined at the top of the tank, just because the plant was 'in their way'. You must decorate their tank exclusively with heavy rocks, PVC pipes, and fake silk plants.

The Houdini Escape Artist:

The Dry Carpet Death. In the wild, they naturally leave their ponds to walk across wet land to find new lakes. In your home, they will climb the filter intake tube or heater cord, pop the lid open with their powerful claws, crawl out of the tank, wander across your bedroom floor, and be found dead, dried out, and covered in dust the next morning. YOU MUST COMPLETELY AND HEAVILY SEAL EVERY HOLE IN THE TANK LID.