Disinfecting a camping water filter without bleach: NOT recommended

I've been trying to avoid bleach, but the Katadyn water filter I use to filter water while camping requires the disinfecting of the filter with bleach before drying it out for storage. I've been using grapefruit seed extract (GSE) instead, so I thought I'd share my recipe and how I came up with it. Disclaimer: My filter eventually got mouldy, so I don't think this works too well, but feel free to try it yourself.

Recipe

Add 100 drops of GSE into 1 gallon of water. Stir well, and pump all of the liquid through the filter. Disassemble and dry. When using again, pump 1 liter of water through it to clear out the GSE.

Why 100 drops? 

Normally, you would use 2 teaspoons of bleach in 1 gallon of water to clean the water filter for storage. So how much if GSE is that equivalent to? For emergency disinfecting of water, you use 1/8 teaspoon of bleach, or 6-30 drops of GSE. Counting with the lower value, we get 1/8 teaspoon bleach = 6 drops of GSE. In other words, 2 teaspoons bleach = 96 drops of GSE. At maximum (counting with the 30), we would get 2 teaspoons bleach = 480 drops GSE... but I don't have the patience to count that many drops!

EDIT: This method DOES NOT seem to work nearly as well as disinfecting with bleach. When I used the water filter later, the water had a funny taste, and upon disassembling, I saw mold growing on the entire filter, and it smelled like a towel that has been standing wet for too long. I don't know whether this was related to the fact that I had disinfected with GSE, but I DO know that in previous years, while cleaning with bleach, my filters always remained perfectly clean and mold-free after camping trips.

Black mold growing in spots. It's too small to see on this photo, but there also are tiny black specks of mold covering the entire filter. The filter should have remained snow-white near the outflow end.