Substrate is pretty dirty but I can't clean it due to plants
So I know that my substrate has a lot of crap in it: small bits of decaying plant matter, probably some fish poop, and maybe a tiny bit of uneaten food, but mostly just dead plants and algae and stuff. How do I clean this out? I can't really gravel vac because of plants being in most places in the tank. I'm thinking of introducing cory cats soon and I don't want them to get sick due to dirty substrate, which I read is a common cause of corys getting infections etc. I'm also worried about barbel erosion in my mix of gravel/fluorite but that's another issue entirely.
How do you guys manage to keep substrates relatively clean for corys, or do you just risk it?