I bought the bigger bottle of hydrogen peroxide earlier today for a 10 gallon DWC tote.
In the bath tub.
I filled the tote up with water deep enough to cover the pump at the bottom of the tote. I kept the air stones in the bottom too. I poured 3/4 of the bottle in the tote with the water submerging the pump. I pulled the pump in and let it circulate for about 15 minutes (or until it stops superficially bubbling, a sign of it killing all the bad stuff)
I then shook everything the water by hand piece by piece to knock everything small and lose off. Sprayed everything off with cold water in the tote and the tote.
Wiped the tote out with a regular towel and filled it with water again to submerge the pump and plugged it in again and let it run for 10 minutes.
Rinsed everything in the tub again and wiped it down with a towel and the rest of the parts. Perfectly clean inside and out: without bleach, only hydrogen peroxide.
I dropped by probes from my pH, temp, ppm monitor in a separate bowl with water and the rest of the hydrogen peroxide and swished them around by hand and then rises them good in tap water.
My pH is a solid 5.8 - 6.4 without any up or down and after putting in nuets. Water temps perfect around 63-66* and ppm for the young ones is around 700-730
Easy, no chemicals and it cleans everything if you follow my steps. No risk to poisoning your plants by not getting all the bleach out of your pumps, lines, tote plastic, etc.