medic63,
The thing about a bio-wheel is that it's sole purpose is to aid biological filtration so it will not make your water any clearer. Adding another magnum may help but if you already have two you could always just use your micron attachment if it ever got cloudy. These things are great, they can remove very small particales from your tank but only run it a couple hours at a time otherwise you will have to buy a new one like every other week cause they get dirty quick and are not as effective..