dirty plants/substrate. Airstone?

Hi guys, my sand substrate and plants always seems dirty with a lot of debris settling down on surfaces. At first I thought it was brown algae but when I took plants out and literally scraped them to make sure they were clean, they looked dirty again after an hour. I'm probably overfeeding but apart from feeding less, can an airstone help to lessen the debris in general? My filter doesn't have a lot of flow because my honey gouramis don't like that and I read that an airstone can help water circulation.

is it a growth of some sort that is getting on your plants (you mentioned you needed to scrape it off), or just debris from the water landing on them? Is your water cloudy?

On first thought, it makes me wonder if you have some cyanobacteria going on in your tank if it grows that quickly, or some type of algae bloom. Can you post some pictures?

It's sediment from uneaten fish food and fish poop that isn't being picked up by the filter. Use a gravel cleaner to suck it out.