Hi I have a pond 3 x 2 metres and 0.6 metre deep. It is well established with plants and has a fountain and waterfall. Water quality tests fine and finally seem to have (no doubt temporarily) won the war on blanket weed. At present it has only 5 small fish in it - 2 comets,a goldfish, a blond goldfish and a shubunkin. Can I add larger fish e.g. larger goldfish and golden orfe or will this upset the smaller fish? Would it be better to add more small fish?