My 150 gallon is well stocked with 10 discus (3 to 6 inches) along with 11 roseline barbs, 11 clown loaches, few cardinals, algae eaters & a large common pleco. My filtration is not elaborate...a hob emperor 400 & a magnum 350 canister.
Not recommended but I've gone over a month without a wc...nor clean the filters. You get caught up with life and can't make time but no problems with the fishes in my tank. I think what helps are the river rocks as substrate. The bacteria within the substrate helps filter the water. I started off with sand but the wastes & uneaten food just sits on top of the sand which was a mess.
They gotta eat so the auto feeder is the way to go if no one is there.