Discus Aquaruim Maintenance

Hi,
I need some advice, I am currently prepareing my 50 gallon aquaruim to
keep about 4 or 5 discus. I hear that you must vacuim the gravel or in
my case sand every week. I currently have 4 Angels in the tank and
each time i vacuim the sand the fish go frantic. Angels get over this
quite quickly, but what about discus?
Another thing what about changing the substrate from sand to gravel
and make an undergravel filter, so all the waste produced will end up
in the gravel filter then just suck everything outfrom underneath,
without inserting anything in the aquaruim.
The waste problem came about when i introduced a Pleco, they are
excellent fish in controling algea but at a price.

Thanks for your help