i personally dont have a guard as of yet because my heater is in between the wall of the tank and my filter (so my filter kind of acts like a guard) so there is no real reason why a spoked fish would get in the gap. When the filter is replaced by my soon to be new external filter i will be getting a cover. Easily made. just a piece of pipe slightly bigger then you heater with lots of holes in it for free flow of water.