I recently bought a mexican dwarf crayfish and everything I have read says that they are very active and won't spend all day hiding, but he just kind of sits at the back of the tank behind the plants. He does move to different positions but then he just sits. I have had him since this Saturday- is he still just adjusting? Should I be worried about him? Is it just his personality? He is in a 20 gallon tank with 6 rummy nose tetras, parameters; ammonia 0, nitrite 0, nitrate 10, temperature 80 degrees. He has been eating a little bit, I believe. Please let me know.