Ok, I have yet another annoying question

. While wiring up my pump relay w/ mostly solid core wire (left over from wiring our house), I also used one piece of wire off of a molex. Now looking at that one peice of wire, it just looks too small. I'll be running a Ehiem 1250. So I just want to make sure the wire isn't going to heat up and melt down too much.
So if you could lemme know if I should swap that peice out for the other stuff, I would appriciate it.