This is the only substrate used. I have a bag of tan pfs I would like to use but trying to separate the crushed shells from the white pfs will be a pain so im trying to lose a little sand each wc. The breeder I obtained them through gave me 2 extra females incase any changed, one did and I lost it but I don't think it was to aggression. These guys are fun, not enough to quit new worlds but definitely fun. The hardest thing is watching out for fry during wc.