[Raf]

If you are not going to run Bio media(aka bio balls, or whatever) then you need to add enough LR to the tanks, 1.5 lb per gallon would do and preferable cured. Then you can just run mech media that gets thrown out every 1 or 2 weeks. IMO, the LR rubble in the filter can turn into a NO3 factory just like the Bioballs do.

In a small tank, you will have a light stocking most likely, and waterchanges are not a big deal as the volume is small, so if you decide against adding so much LR or adding any at all, the bioballs or wahatever other biomedia won't be such a big deal, you will just have to monitor your N03 more carefully.