tiny little white spider things and little brown hard shelled worm things in soil

I topped up one pot with my soil mix that is damp and theres all these little fucking spider things in the soil. should I just drench with h202, it's $4 for 100ml of 3% here and hard to get the stronger stuff, or is there a cheaper way? I think it's limited to one 'four week old' plant/pot.

Maybe take a picture if possible. If not spend some time on internet trying to figure out exactly what the "spider things" and "worm things" are. Google image search can be a help at times.

Anyway they might not be harmful, but if they are you are going to want to know exactly what they are in order to apply the right treatment. Otherwise whatever you do may not work at all, or be harmful to the plant.

And if it's limited to one plant I'd isolate that plant from the others ASAP to prevent them spreading.

look up hypoaspis miles. Helps on a number of bug problems.

Early detection of spider mites, before damage is noticed, is VERY important. The tiny spider mites can be detected only by a full and thorough leaf inspection (on both sides of the leaf). If you find Spider Mites you must act fast and hit them hard.
The thing about spider mites is they are very quick to take over your plant, and even quicker to evolve and adapt to whatever methods you are using to try to kill them. They will soon develop resistance to almost any method you use to get rid of them.
If you have problems with spider mites, keep a constant and varied offence for the best chance at success.
If you already have an infestation, start hitting them hard with something that will kill them on contact.
Follow up in 2-3 days with something different that kills their eggs as well as a different method to kill the remaining adults (these ones will already be more resistant to your original method).
Repeat those two step at least one more time to ensure that you have really cleaned out your grow room.

Cutting up habaneros and sautéing them in water has always worked well for me for pests.

I always spray it on the leaves, tho, I've never treated soil with it. I don't think it would hurt the roots, a bunch always drops off into the soil when I treat.

I've never had that serious of a problem with pests, tho, so itight not work for a serious infestation. Good luck crit