Choosing Ornaments That Are Safe in Water
Aquarium-safe is a real specification, not marketing language.
What makes resin safe
Aquarium resin is inert once cured and carries no soluble dyes or metals. Garden and craft resin is not tested for submersion and may leach.
Avoid sharp edges
Anything a fish can swim through must have smoothed openings. Long-finned species tear easily on a rough moulded edge.
Rinse, do not scrub with detergent
New ornaments need a rinse in plain water. Soap residue is far more dangerous than the dust you are trying to remove.