Thanks for help, Diana. Over 20 aquariums? Someday...that'll be me
I decided to redo the stand 1 brick high so it would cover the full 18" of the tank's side. You guys are right, I just didn't want to put more weight on my second floor with more blocks so I had to figure out a compromise. So it's now 4 cmus or cinder blocks on the ground in a U shape if that makes sense. Then the wood planks and then the plywood. I started putting in the substrate and plants today. It'll be an emersed setup for awhile.