An earlier post in this thread by Kevin may be helpful to you because of his experience with guppies...my set up is a complete aquarium gravel substrate, and a pump that is in a sectioned off area so it can be pulled easily and the critters cannot get sucked to it. I only have the one FB and the fish are Endler Live Bearers. Look them up...they are really colorful and there are websites devoted solely to them.The live plants I have have been a matter of testing which ones can stand their feet in the water...and the tank has a waterfall that plays over the mopani and java moss...there is no filter but I do small water changes every week and the waterfall adds oxygen. It was not intended for critters but I am delighted to have had this door open by the sheer gift of a stowaway on some plants that arrived at Lowes to the plant department...have searched the internet over and over but cannot identify it. So I got hooked...