I was just looking in to the tank and a spider must have somehow fallen in there, and now one of my tetras has it hanging out of his mouth...Would it be a good idea for me to try and get the spider out of him before he eats it, or should it not do him any harm?

I live in Nova Scotia, so to the best of my knowledge, there are no poisonius spiders around here.

All spiders are poisonous, but as far as I know, most of them aren't harmful if swallowed. A few spiders have gotten in my tank, and usually get eaten without a problem.

Well he seems to have let it go as it's now halfway sucked into the filter. I was just a little worried cause i've seen people on here mentioning that they've fed their fish different kinds of insects before, but i've never seen someone mention spiders before.

If the tetra let it go, it's probably too big to swallow and they gave up. If that's the case, I'd take it out just so it isn't decaying in the tank.

It wasn't an a very big spider, but the tetra himself isn't very big either. He had it hanging out of his mouth for a good 10 minutes, then just gave up I guess. I was debating knocking it off the filter and moving it over to a corner of the tank to let the Cory's feed on it, or perhaps the angel fish if he found it, but decided to just scoop it out instead, because as you said, I didn't wanna risk having it sit there and decay.