I do regular large water changes on all my tanks. I don't have a specific day that I do each tank, so there's some flexibility in my schedule. Tank 1......moderately planted, 72G with 11 full grown discus, a few cories, a handful of tetras, a few amano shrimp, it's very low light so fast growing plants die, HOB filtration which has no problem processing all the ammonia these fish produce. Regular river gravel substrate, very, very deep. Most often I have 10-12 ppm nitrate coming out of the tap. They are not overfed, their main daily meal is worms, there is no accumulation of decaying food in the substrate. And after an hour you'd be lucky to find a worm in that tank that had beed missed. Over a period of 8-9 days my nitrate level in that tank is at least 40ppm. So to reduce nitrate levels, I do a water change and do some gravel vaccing in the open areas. The thickets that are planted around the driftwood are left undisturbed. A lot of the discus solid waste finds its way to the plant thickets and supplies nutrients for the plants. I do not add plant food. If I had fewer discus in that tank I would change the water less often. But I choose to have more discus so it is hard to keep the nitrate level down. Could I stretch the water changing routine out longer? Sure. I know that nitrate at even 80ppm isn't going to cause the discus to keel over. If I have a busy schedule where I know I'm going to be hard pressed to do a water change, I cut down on the feedings during that time thinking that less food will result in less fish waste than normal.
My 75G heavily planted tank with standard HOB filtration, river bottom gravel, contains somewhere around 6 full grown bristlenose breeding plecos and 6 subadult bristlenose plecos along with some ember tetras, a dozen cories, some cherry and amano shrimp. It is very hard to control the amount of food in this tank given the number of bottomfeeders, trying to balance keeping the adults in breeding condition and the providing the subadults the food they need to continue to grow well. There is a much higher accumulation of uneaten food settling into the gravel with bottomfeeders. There needs to be enough food so that they all have access to it. I still feed that tank twice a day because of the young ones growing. In this tank the nitrate is not the issue it is the accumulation of uneaten food trapped in the gravel. I could avoid it by cutting down on the food. I realize the fish do not have access to this quantity of food in the wild....but they can constantly swim to another area where there is more biofilm to consume, more algae to eat, natural food that their river supplies that my enclosed tank cannot. They always all come out to the front of the tank when I do add food. They have no way of getting down to the trapped food so water changes with gravel vacs take care of the uneaten trapped food. If I was home all day instead of out of the house for 11 hours at a time, I could drop less food in more frequently, in fact that is what I do on weekends. I only gravel vac in the front and along the two sides of the tank to get any leftover food up. The rest of the substrate remains untouched, the plants are so thick you couldn't get to it anyway.
My growout tanks for the pleco fry and the cory fry get filthy from the frequent feedings necessary to keep them growing nicely. In their natural habitat they would not have the abundance of food in any one spot, but they do have the abiltiy to keep moving over the river bed to find more. In the tanks they are limited to the 4 small sides of the tank. Feeding 75+ pleco fry blanched zucchini in large enough quantities so that a lot of them can even get onto a piece of zucchini creates a lot of slimey film in the tank and the filters. They only way to get rid of it is to do a water change and clean the filter. After a week of feeding blanched zucchini in an 84F tank.....let me tell you, those filters aren't a pretty sight.
I have a 55G moderately planted tank with only a trio of adult breeding bristlenose, some ember tetras, otos, cories and cherry shrimp. The water and substrate does not get messy quite so fast in this tank because there's no juvenile fish to feed and having only 3 plecos requires many less chunks of zucchini per week.
So except for my discus tank with the higher nitrate levels, I am doing routine water changes to clean up the mess made by keeping the "barnyard bottomdweller pigs" of the freshwater tropical fish world. Less fish requiring less food = less work for me, I know that. But I'm raising some awesome fish that are in very limited supply worldwide, some are not found in the wild today, and am able to provide healthy specimans so that other hobbyists can enjoy them as well. And I'll be suffering pleco and cory breeding burnout in another year!