I usually stick with Discus and Angels but have recently acquired two pairs of agassizi's dbl reds, one pair of which has bred underneath my nose.. Now I'm setting up a tank just for the 5 apisto's and 5 German Blue Rams. Typically, I use PFS for my substrate but with these two guys, being substrate spawners, should I set this tank up with fine gravel or stick with the sand? Bill in Va.