First, you'll definitely need the scoop! I've tried divided substrates in quite a few planted tanks. I swear my fish pick up the sand in their mouths and spit it out on everything (dwarf cichlids
). I find sand on top of the driftwood at times. I also get tons of the gravels bits (SMS) in the sand constantly. Black gravel bits in white sand, just oh so pretty. With cories you'll have just as much rooting about in the substrate. Even when I divide the two substrate areas w/ larger driftwood; those fish still mix it up.
My best advise: forget about it! Unless you really, really
love the look; and
love the extra work tending to it. Otherwise, pick just one and be happy.
If you go ahead anyway, be sure the two have significantly different grain sizes. If the larger bits in the sand (PFS) match the smaller bits in the gravel part ( SMS, Eco-complete, Flourite, etc.,) you won't be able to separate them back out with any type of sieve. Hand picking, you will be. Yeah, sigh
, I got so tired and mad at one tank, I yanked the divider and stirred it all together into one salt and pepper hodge-podge mess. (The SMS being lighter weight and larger-grained actually ended up on top - mostly. Except when I replant, then it burps up white sandy knolls.
I used plastic Quilting template purchased at Jo Ann Fabrics. Cost around $4.00. It cuts easily with scissors to the depth needed. I don't bother to silicone it. The weight of the two substrates seems to keep it in place.