I was warned that gravel causes many probelms and is associated with bacteria and sometimes poor health. I have not used gravel for some time, Mr.T is very happy and the tank doesn't smell like it used to.
Also, the pet shop gave me a brilliant idea. Use a clear hose about 5 ft in length, fill it with water and funnel out any crap from the aquarium into a bucket. Works like magic! AND couldn't be done with gravel in the tank.