pinks and blacks reach the same size, theres nothing different about them other than their colors.
sand is a great substrate for them as both male and female like to "sift" around in it to kick up leftover food for the babies, plants are also good..the babies like to hide and rest on them..and obviosly..cover..bogwood..driftwood..overturned flowerpots...all work for cons...if the tank was bare..they would still spawn..but cover is better.
good luck with them..they certainly are fun to breed.