I am retuning to the hobby after a 50 year hiatus. I find there is a lot of new things in the hobby. Hang on filters, canister filters and glowing fish. My plan is to set up a 15 gallon tank. I plan to plant it heavily with one or two mystery snails, 6 guppies, 2 corydoras, 1 pleko and 10 shrimp. I plan to have an under gravel and foam filter, no heater. I have a question. Can you place aquarium soil on top of an under gravel filter?