I don't want to belabor this, but a 6g tank is simply too small for any tetra species [except a dwarf like the Ember]. The fish may be 1 inch now, but if they are in the proper environment they will not stay one inch, they will attain close to 2 inches. But not in too small a space where water quality is as much an issue for the fish growth as is physical space. And there is the need for "space" around the fish as Barb mentioned.
The inch of fish to gallon of water is another myth in the hobby. By that rule, you could keep a 6-inch fish in your 6g tank; but such a fish would scarcely be able to even turn around, and the deteriorating water conditions would likely kill it in short order. You could keep a horse in your bedroom, and he would "exist" and remain alive--but is that adequate space? No. Same thing here.
We want you to be successful in the hobby, and we care about our fish.