Try going to a rock farm. (place where rock is sold) They will probably have a pile of broken pieces of rock that they will sell cheap. I got the rocks for my 55 gallon tank at 35 cents a lb. Compared to $1.99 per at the fish stores. Same stuff but a lot cheaper. They will also have more selection for color.
Message to all aquariasts!!!!!
Anyone who lives within their means suffers from a lack of imagination.