Dirty Gravel

what do you mean by dirty...leftover food and fish poop, or is something growing in or on the gravel? how much filtration do you have in the tank? fake plants or real? how long has the tank been set up? what other fish are in the tank?
 
One thing the corys do that does help is they stir up stuff. My shrimp do it too. As soon as I added both my water had a lot more stuff floating around for the filter to remove BUT I still have to vacuume when I do water changes every week.

Q
 
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