lava rock as base substrate

[youdontknowme]

so.. i have heard about anaerobic at the soil.
so by putting lava rock as base substrate , will it prevent anaerobic condition from happening ? since it will be more oxygenated.

for the substrate im going to use ADA new amazonic.

the powersand is too expensive for me , 2L cost 38bucks here in this country.

and by the way , what are the recommended soil depth for planted discus ?