What+it+affects

Without substrate many stream creatures like the fresh water sponge and algae would have no were to live.

Different types of substrates help some species but not others.

not one particular substrate is better than the other.

fish that like to dig for shelter like puffers prefer sand, but species that like to use substrate for protection, like crayfish, gravel would be better.

The fresh water sponge live their entire life attached to the tops and sides of rocks.