More water changes, clean your filter, clean your gravel.
I have a sponge filter with some moss growing on it should I remove the moss?
Do I just keep doing water changes everyday until it hits 10ppm? I also use sand
Everyweek its a small 10gallon I do about 50%
You may be overstocked then? I would do 75% a week and see if that brings it down.
I don't think so I only have two dwarf puffers in the tank. It could probably be the snail population then
Puffers are messy, when I had my dwarfs they would leave half eaten snails rotting. I would look for stuff like that.