Hi, Since getting new fish I've decided against any substrate at all, although I do have plants and decor. It looks so much cleaner in there, the water is crystal clear and it's so easy to clean. Also, no algae. My fish still forage around at the bottom looking for food so I don't think they're affected by the lack of substrate. Also, they were in a substrate free tank (at the pet shop) before I got them so they don't really know any better? Your personal preferences & thoughts?