Can you use roof slates for water falls? Will they harm my Koi? -Rob

I assume that you are talking about actual slate, and nothing like fiberglass or asphalt shingles. Slate itself is harmless to Koi, so you should be fine with using them in a waterfall. Absolutely make sure that there are no anti-mold or any other chemical treatments that are applied on the shingles. The chemical treatments could poison your Koi. That is not really the desired effect of a new waterfall. Here's the blurb from Wikipedia on roofing slate: Slate can be made into roofing slates, also called roofing shingles, because it has two lines of breakability: cleavage and grain. This makes it possible to split slate into thin sheets. Fine slate can also be used as a whetstone to hone knives. Because of its thermal stability and chemical inertness, slate has been used for laboratory bench tops and for billiard table tops. In 18th and 19th century schools, slate was extensively used for blackboards and individual writing slates for which slate pencils were used. Slate tiles are often used for interior and exterior flooring or wall cladding. Tiles are installed and set on mortar and grouted along the edges. Chemical sealants are often used on tiles to improve durability and appearance, increase stain resistance, reduce efflorence, and increase or reduce surface smoothness. Tiles are often sold gauged, meaning that the back surface is ground for ease of installation. Slate is often used as a decor in freshwater aquariums. Slate will not alter the chemistry of water {except in the slate containing feldspar which may leech silicates into the water resulting in excess diatom growth in marine aquaria). When broken, slate produces a natural appearance while remaining relatively flat and can be easily stacked. Silicon glue adheres to slate, creating a non-toxic bond to secure it. It is also used in stairs and pathways for the same reasons. Slate. (2007, February 18). In Wikipedia, The Free Encyclopedia. Retrieved 20:26, February 19, 2007, from http://en.wikipedia.org/w/index.php?title=Slate&oldid=109060524 Share: Del.icio.us Digg Reddit