Anyone know what this is?

Looks like a ground probe.
Linky:  http://images.marinedepot.com/ps_Vi...ory=FIMIGF

 

Yep ita a grounding probe. You put the end with the suction cup into the tank, or sump, and plug the other end into the socket. You the take the little wire and put it under the screw that holds the cover on. This way any stray electricity is pulled out of the water. Shaun

 

Quick question? How many people use a ground probe. I was thinking of getting one just to see if it makes a difference. Is it worth having or is it just one of them extra things you really don't need.

 

I had the same question not too long ago, found a thread on RC about it.

[class="nf"] Grounding probes: Hazard or helpful?[/class]
HTH