hey, everyone, your advise would be much appreciated. what else can I add to my 55 galon tank (4ft x 18 inch x 15inch). I currently have an angel (4inch head to tail by 5 inch fin to fin) which is quite dominent and won't take to other angels, a krib which is quite placid, 4 yoyo loachs, 7 black neons and 5 rummy nose tetras, what else can I add to this tank that won't upset the tank but with abit of size