Also the top as said by twh is plastic,Its a similar type of material that coats it as formica thats used in bathrooms and kitchens. the coating makes the top (and bottem) waterproof, and its super easy to keep clean if it gets dirty. And it looks clean overall.

You can order Black melamine from your local Home improvement store, but its double the price of normal melamine, But if your set on black then its worth it. Also, just a note, depending on the size tubs you want to use, Home depot sells pre-cut melamine shelving, like to use in a shelving system that is colored, and can be wood colored, or white, ive seen a few other colors, maybe black was there, but its worth checking. Its over in the area with the shelves (wire and the melamine systems).

One other note is that you want a tablesaw to cut it that is good and fast, as it chips easily.

Besides the weight, it does seem to work great for cage building and racks, I use it on the floor of my Dragons cage and though its not exposed when something hits it its really easy to wipe free.