Although in captivity, this territorial aggression has never gone, and thus becomes one common reason why the fish are unable to cohabitate with other tank mates. (practical-pet-care.com)
It's not an aggressive goldfish breed but is a fast swimmer with a big appetite and so the wakin goldfish isn't a good tank mate for any slow swimming goldfish breeds. (caringpets.org)
There are lots of fish that could be kept in the marine aquarium, some of them for advanced aquarists, some not suitable for reef systems, some over aggressive with care needed in selecting tank mates and others of course suitable for beginners. (aquaristsonline.com)