Don't use particle board ofr high humidity areas. Basically anything near a tank. When it absorbs the moisture it expands, much like a napkin for instance, contorts, and generally looks like it has become a pulpy tumor.
The wood itself is probably safe unless it has been treated. Why doesnt he/she throw some contact (plastic linolium like sheet - sticky on one side) or some waterproof paint or even wrap in plastic sheet.
That's how I made my cover for my large sump. Wrapped OSB in a double layer of 6mil sheeting. It's not the prettiest but it's just a sump and out of sight.
I would think it's not the greatest thing to use and it won't last very long. Even if it's wrapped in laminate, it would most likely start to warp. But, it would protect any of the glue that that use to make particle board from making it into the tank.
Have him go to Lowe's and get a cheap piece of acrylic cut down to fit the tank.