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Are crayfish good or bad to keep in the tank with a RES?
The crayfish I caught was smaller than my RES, Vincent.
However, Vincent never ate or tried to eat him.
So, I left the crayfish, Mr. Claws, in there, and I figured he would clean the tank somewhat.
I want to know if it was possible that the crayfish actually helped keep the tank clean and prevented disease.
º(ô,ô)º

I say they're bad, because eventually they will get eaten.

Not a good idea. Check out this post:

http://www.redearslider.com/forum/viewt ... ++crayfish

Your turtle could get hurt - crayfish are pretty tough too.

Anything added to the turtle's tank equals food, so in my opinion you should only add safe things ( i.e rosies). A crayfish can fight back a bit better and you don't want an injury, that could lead to a terrible infection.
I've found that filters are your best and only bet for a clean tank- cleaning fish and/or snails just don't last long enough to do any good... and in some cases they add more to the waste than they remove.

Thank You for your opinions. I really found them helpful.

I just found out the hard way about crayfish. I just got back home from class and was checking out the tank...One little, Two littl..."WAIT, 1?!?!"

Reading this post I've come to the conclusion

3 Turtles + 1 freshly molten crayfish = $2 mini lobster dinner

If you are looking for a tank detritus cleaner that your RES can eat, I would recommend ghost shrimp. They are great scavengers, and great live prey for your turtles. They are usually less than a dollar, so if they get chomped it isn't such a financial loss. They are also very pretty, they have clear bodies and are fascinating to watch. i would recommend a few bottom plants and rocks as hiding places for them, or the turtles might have an all you can eat shrimp buffet!