I definitely agree with whoever suggested using the extra real estate in all of those tanks to grow out some various mosses. You have the room already so tossing mesh tiles and waiting for the moss to grow won't really be a problem since it is just a bonus for you.
Plus mosses are great for fish fry usually.
I not familiar with mosses at all but since so many people are saying great things about it i guess i have to give it a shot. Lol