Gravel recommendation

[FortMyersSteve]

I have a dirt substrate that includes some peat moss and manure, which I want to keep for plants and other reasons. But stuff floats up and clogs my filter. I think I'd like to put a layer of small stones on top of it to stop this. Larger than the typical 2 mm aquarium gravel, though not huge. Best colors would be brown, black or tan. Most important to me is that there are no synthetic colorings that might leach into the water. Can anyone make a recommendation of a specific product, or a link to a vendor or place to search?

 

[ZxC]

You didn't cap the dirt before filling the tank?

Any aquarium gravel will work.... Black Blasting sand, Pool filter sand, Eco-Compelte, Flourite etc. etc. will all work