Is this tank stocked well?

In my opinion it's to many fish. I would maybe cut back on the guppies or just get 4 or 5 neons. If they are young fish then you are probably fine. But, you may have to upgrade in the future. I don't think you will have any agression at all but, watch them when they're adults there might be a little agression. Since I can't keep guppies alive for more than a couple of hours or days (ph very low, dh very low) I cant tell you how much waste guppies make. So the biolode might be fine.