My fish tank has been cycled and I have 3 fish and a shrimp in the tank it is a 30 gallon tank. All the fish seem fine no signs of any problems at all. I have noticed on the glass there are these white spots. They are very small and seem to have a bit of a web holding them on the glass. They kind of look like dried salt but they are in the tank. Is this an illness or just nothing. I did not check the parameters today but yesterday they all checked out fine. The hydrometer reading is between 1.022 and 1.023. That has been steady for a week. Any thoughts?