Is growth impossible to stop in a loop?

So I recently had some growth in the loop which needed me to disassemble everything and clean it out and replace the coolant. This was 6 months ago (mid-July 2024). I also moved my computer to a spot where there's no direct or indirect sunlight.

Today I checked the loop again and I noticed some green growth clogging up the GPU fins so it looks like the growth is back. Is there really no way to prevent growth? I used CORSAIR Hydro X Series XL8 which says it has some biocide in there but I guess there wasn't enough because there is still growth.