I know … I know … “Marine Aquarists Association …” However; I inherited a disgusting 15 gal. Eclipse fresh water setup with under-gravel filter and 4 inches of gravel as substrate. Previous owner did not run any mechanical, chemical, or biological filtration and I got that all up and running again. I’m cleaning it up and am wondering yea or nay on the under-gravel filtration. The Tubes are encrusted in disgusting, gross junk and it would be easier to just pull them out. Under Gravel important?