Best Dirt Cap
I am planning/hoping to set up a new 20L dirted tank in the near future. I am wondering what would be the best cap for the dirt would be. I am trying to decide between sand, gravel, or a planted substrate such as eco complete. I think a sand such as Black Diamond Blasting Sand (BDBS) would look nice, but I worry about it sealing off the dirt, preventing air from escaping and also preventing organic material from getting down into the dirt to be broken down. In Walstad's book, she recommends fine gravel, as it allows thing like fish food and fish mulm to get down into the soil, where it can be broken down and used as fertilizer. My problem with gravel is I can't seem to find much that is a fine grain and nice looking other than Carib Sea Super Naturals, but that costs more than Eco Complete on amazon. The final option would be EcoComplete or a similar substrate, which from what I understand is a good substrate because it is good at breaking organic stuff down into nutrients for plants. Also, how much of anything would I need for a cap of around 1" of the dirt in a 20L? Would 20lbs be enough or would I need more.