Hi I am looking for some cool fish that are good for clean up crew. I have a 20 gallon tank with one gourami and 3 zebra danios. I really want cory catfish but I don't think I can get them because my gravel is not smooth, i think? Post some pictures on this if u can on here of your gravel and tell me if it is smooth or if it is not so I can get a better understanding at where mine is at and give my ideas of other cool clean up crew fish please. Thanks.