Just got back from 1 week vac and my pool looked like this with stains all over the bottom.
I did a backwash on my sand filter and let the vacuum run for 24h.
I also checked my chemistry and everything seams in order:
Unfortunately my water looks very cloudy right now and the filter doesn't seam to filter the small particles very well that have been stirred up from running the vac.
I ordered De after reading thorough some of the advice
I hope somebody could let me know how to get my pool sparkling clean and also for future reference how to prevent the residue on the bottom (more frequent vac).