I used to like no gravel as in a bare-bottom tank. But now, they look too bare and less attractive. I'll always have sand or gravel now. prefer sand though.
i prefer play sand, a lot of people stay away from it because it's hard to wash...but it's just a one-time rinse. yeah it took 20 rinses in a 3g bucket to wash about 35lbs lol
it's annoying with a HOB though...if i touch the sand near the hob without turning it off first it starts making noise. leave the sand alone and it'll be fine