Decorating and furnishing your freshwater aquarium is a fun (and beautiful) way to provide enrichment for your fish. You can buy premade items from a pet store or create your own sculptures. However, many materials available at a craft supply store can be toxic to animals. Before you add any homemade materials, be sure they're pet-safe.
Avoid Air-drying Clays and Polymers
Any clay that can be shaped when wet and then air dries to harden is unsafe for aquariums. When submerged in a tank, these sculptures will reabsorb the water that was dried out and turn back into soft clay that could be ingested by fish.
In addition, polymer clay that is hardened by baking is also unfit for freshwater aquarium use. Water submersion will cause these sculptures to deteriorate and fade, leaching toxic chemicals into the tank.
You can create aquarium-safe sculptures by using ceramic material, then glazing and kiln-firing the piece twice before adding it to the aquarium.
Use Premade Ceramics and Pottery
Any piece of premade fired ceramic or pottery will be safe and non-toxic for fish tanks. You can use tea cups, coffee mugs or unused terra cotta pots to construct a fun playground or cozy hiding spot in your freshwater aquarium. Always wash these items before adding them to your tank. Avoid using any items or parts of larger items that have rough surfaces or sharp edges that could possibly scratch or injure a fish.
Avoid Paints and Stickers
Most plastic, glass and ceramic sculptures are fine to use in freshwater aquariums. But before you add anything to your tank, always check if there is any paint that chips off easily using a fingernail. If it comes off easily, try soaking the item in a separate container of water overnight, and scratch off the rest of the paint. If the paint does not come off cleanly, do not put it in the aquarium.
Be Careful with Natural Materials
It may seem like a good idea to add natural material to your aquarium sculpture garden, but some items can be unsuitable for freshwater fish. Never add seashells picked up off the beach or sticks found in the woods. These items can often carry parasites that are foreign to freshwater.
You may use smooth stones and rocks that have been washed carefully in hot water, and covered in a silicone aquarium sealant. Do not use sealants that are meant for home improvement projects.
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