I'm not sure about the substrate it is likely not necesary, I have a special african cichlid substrate like a fine gravel. It is mixed in with my sand (mostly sand-playsand) it looks fine but is a pain to clean, actually I pretty much don't even bother vacumeing it because of this. It may just be the sand (my only sand tank), but to get any crap up I have to put the syphon almost in the substrate. You should be fine with out any buffer, do you know your ph? and if you want to use something the gravel should work fine in your cannister, I have some in my fluval 403, buy a fluval bag filter bag,
The cichlids will also prefer the sand.