IMO husbandry issues here. If you noticed a white spot that turned into longer algae you are not cleaning your glass enough. Do you have a magnetic glass cleaner? New tanks require this almost daily.
Nassarius, Cerith and Florida Fighting conchs to clean and shift the sand around. A red scooter blenny is actually a Dragonet, like the Mandarin, and live off live food - copepods - and are exteremely hard to keep in a small system like yours. They are not sand sifters.