Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Well, Java Fern and Java Moss are not rooted in the substrate, so if you stick with these, the substrate is not too important. Play sand is fine, or there are some other colors available in different products like black diamond blasting grit or Pebble Tek quartz.
If you want any rooted plants, however, it would be important to get a good quality substrate. Something with high cationic exchange capacity. This need not be expensive. Something like Safe-T-Sorb, for example, is sold in 40 lb bags and that is enough to do about 2 tanks with the traditional 55 gallon footprint.
That size tank is tricky to deal with, to get a good 3-D effect because it is not very deep back to front. I would do something rather simple, a couple of bunches of Java Fern and tie the Java Moss to a simple curving branch. Don't get wood with too many little twigs. Maybe 3 main branches, just a couple of forks. Keep it simple.