hey guys, I have a pair of RTC and a pair of Iridescent sharks since they grow about 4 feet long I have decided to build a monster pond for them. I have a lawn edging with bricks where there are full of grasses and plants, etc (I am going to renovate it into a pond). The dimensions are 15x5x3 feet. Could you guys suggest some more fish and also could you suggest ideas about the pond filtration?