How to Create Your Own Aquarium Decorations


Did you know that you can make your own sea floor decorations for your aquarium? With some molding work, you can create colorful coral reefs, rockscapes, and more with a few simple steps and molding material. This is a cheaper alternative to buying pre-made decorations that may not be aquarium safe. Making your own custom reefs and sea sponges also eliminates reef harvesting, preserving the sea life’s natural habitats.

Here are the main ingredients and tools you need:

  • Silicone for molding
  • Silicone rubber
  • Pigment of your choice
  • Plastic mold wall
  • Measuring cups
  • Knife

You can purchase these silicone molding making supplies from your Raw Material Suppliers.

Preparing the Model

For the sake of this tutorial, we will be making a sea anemone model. If you do not already have a model, you can make your own with non-sulfur clay. Place your model on a base which you will use to hold your mold. Use a plastic mold wall that leaves at least half an inch on all sides of your model.

Silicone Mold Making

For this step, you can follow the directions we listed in a previous blog. But generally, you’ll be mixing two parts of your silicone blend. After thoroughly mixing in a mixing cup, you can start pouring into a single spot in the plastic mold wall and let it rise over your model. Let the mix cure for a certain amount of time depending on the mix you use. Magikmold GT-6142 Tin Cure RTV Silicone has a standard cure time of 12-18 hours.

Cut the plastic mold wall down the middle and separate it from the mold itself. Be sure to lift it off your base. Use a knife to cut open your mold just enough to lift your sea anemone model out of it. Do not cut all the way down.

Casting Silicone Rubber with Pigment

Before molding a silicone sea anemone model, you must prepare your mold with a release agent, otherwise your product will not release easily. Reseal it with rubber bands. Repeat the mixing steps for creating a mold using RTV-50 Platinum Cure Silicone. Mix in the pigment of your choice into part B before stirring in part A. Pour the colored mix into the mold and wait for it to fully cure.

Final Steps

Slowly pull the mold apart at the cut seams to release your sea anemone model. Pull the model out slowly so the tentacles don’t snap off. Your aquarium decoration is ready to adorn your fish tank!


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