most people will tell you to be completely safe when putting a new frog into an old habitat to completely remove everything and either clean it or replace with new stuff. If you want to be totally safe then redo the whole thing. Personnally i would go to petco since its $1 a gallon sale right now and pick up a 20 gallon for the tree frog as well and turn the 10 gallon into a quarantine / grow out tank for any future frogs.