I currently have a 55 gallon tank with one turquoise severum, one red spotted gold severum, 4 giant danios, and 3 tiger barbs...is there any room in this tank for a smaller pleco (such as a bistlenose or gold nugget) or possibly a group of smaller schooling fish to fill out the tank? I have two Biowheel 350's running on the tank and do 30% weekly water changes.