I have to be on my guard at all times when my hand goes in. my 13.5" male dovii packs a serious bite. I think he likes the taste of my blood. When I see them coming close, I usually push them away, and they'l back off for about 10 secs. Also, I have found putting my whole arm in the tank quickly reduces the chance of a bite. I also have a towel to hand to dry my hair, face, and neck, and my arms, just from lifting up the lid to feed them, and sometimes I'll have to change my clothes. They are insane fish, but its all part of the fun.