relies upon a great deal on what style of fish/animal you have in it, what share, how vast the tank is, what style of filter out, and extra. maximum individuals advise gravel using fact it rather is yet another place for reliable micro organism to strengthen. some fish go with sand to dig in, so substrate is a ought to. on the different hand, in case you have something rather messy, which include a turtle, or a sort of fish conventional for eating gravel, then gravel is a no-no. no remember what you nonetheless ought to vacuum the backside of the tank, whether there is no gravel gunk will flow to the backside. I choose gravel in fish tanks using fact in my view i think of it seems extra valuable.