I don't what to make LR, but what to make some things that will not effect my tank, what is the best to use, porcelain, clay, cement, or any other suggestions. I must be able to mold it.
Maybe i got it wrong ; but i get the picture that Sean is wanting to create some type of structure for his reef, with a reef safe material
Nope not polyurethane. Normal plastic milkcrate that can be cut and melted with a heat gun to create a reef rack.