When changing the water in my 30g tank this morning, I noticed an infestation of little spider-like bugs on the surface of the water and along the walls of the tank above the water. These bugs appeared concentrated around the little anacharis leaves that stick out above the water's surface.

Is anyone familiar with these pests? What's the best way to get rid of them?

I'm going to start by making sure all of the anacharis is submerged and not letting any of it float.

It sounds like some kind of mite. Not harmful, and as you mentioned, keep the plants submerged and that should get rid of the bug. I would wipe them off the side of the tank and try and scoop any up that I can see. Also, you could drown them.

do they look like red spider mite?

Does your goldfish eat them? The bugs i mean.