One word of caution with decorations (or anything in the tank): unlike other
animals who know enough not to try and get into a small space because
they'll get stuck, goldfish are just dumb enough to try. Stay away from
anything a fish can potentially swim under, behind, into and get stuck. I
used to have fake grass that rose up about 1/3 inch and then spread out
horizontally and was unmovable. That small space was just enough for "Mr
Boots" to meet its demise in.

Oh well,
E.Otter