When i set up my cichlid ttank it took agggges and multiple washes out of the filter sponge before it settled. I ended up having to go the aquarium and get heaveier sand to put on top of it. It will settle. You just have to be patient. ive found that having an extra layer of cotton wool in my filter and not putting my "water into the filter" pipe so close to it, it doesnt stir as much. I wash the filter out every couple of months and its never on the same day i do a water change.
The other thing i have learnt is that with sand my cichlids love to spit it and throw it everywhere so i have to also wash my silk plants and decor or they start to look dirty and festy.
Just be patient. I have crystal clear water now.