Should I be worried if my hermit crabs are pushing each other?
No. Hermit crabs are rather strange animals. Although it would be much easier for them to walk around another, they prefer pushing each other out of the way with their claws or climbing over each other. Most hermit crabs are not harmed at all by such pushing and it does not mean that your hermit crabs hate each other.
Should I be worried about shell fights?
Yes. Shell fights often lead to streaking victims. Incidents of shell fights can be removed by keeping plenty of spare shells in the tank, especially copies of the ones that your hermit crabs are wearing. You should always intervene by separating the aggressor and victim into separate tanks whenever you witness a shell fight occurring. Signs of shell fights are listed below.
The aggressor keeps following the victim around the tank.
The aggressor wraps its legs and claws around the victim's shell and does not appear to want to let go.
The aggressor starts rocking the victim's shell back and forth.
The aggressor starts poking and pinching at the victim's body.
The victim starts rubbing its legs and claws together to make chirping sounds.
What should I do after stopping the shell fight?
Check that the victim is unharmed. It is up to you whether the aggressor or the victim gets put in the isolation tank. If the victim is unharmed, then put the aggressor in the isolation tank with plenty of shells resembling the victim's. If the victim is streaking or has lost limbs, put it in the isolation tank instead.
When can I put the aggressor and victim back together in the same tank?
You should keep the two hermit crabs apart for at least three days. When you do put them back together, place them near each other to see if the aggressor still wants to harrass the victim. Keep checking the tank frequently for another three days. If the aggressor has lost interest in the victim's shell, then you should not need to worry anymore. Otherwise, if the aggressive behaviour occurs again under your supervision, put the aggressor in the isolation tank for a week. Repeat this process until the aggressor loses interest in the victim's shell.