Naturally, no. But one would eat the other's fry. DONT PLAN ON PUTTING THEM TOGETHER! They will require different temperatures and diets to maintain.
No, but they would eat each other's young
They might have fought each other.
Two males will kill each other.
you can not keep two males together as they do fight each other
Liolik answers: The Siamese fighting fish
They were probably fighting with each other.
Heck no! I would highly discourage tanking common goldfish and Siamese fighting fish together. I have one of each myself, and they each have their own personalized homes and feeding/water changing schedules. Bettas are called "Siamese fighting fish" for a reason; the males are highly territorial and are fit to kill. A couple times a week I'll hold a mirror in front of my betta and he shows all his fins, and tries to attack his own mirror image. It is not good to do this for too long, as it will wear them out. Common goldfish are referred to as "feeder fish" because they make great meals for larger carnivorous fish. Though male bettas aren't very large, they are still carnivores.
Females will get along with each other. Don't put males together or they'll fight to the death.
Goldfish to not kiss each other. They may play, or bump into each other, but they do not kiss.
It's not uncommon for goldfish to hang around each other in a tank; sometimes they don't bother with each other, and other times they are bumping into each other.
they will pay attention to each other
If you refer to a Siamese fighting fish (betta), they are territorial toward each other. They will most likely fight each other if there are more than just one in the same tank. It must be avoided.
Male Bettas are commonly called "Siamese fighting fish" because they have evolved in the wild to drive any other male of their species away from their territory. If two are placed in the same container and neither one can get away, there will obviously be a fight. The practice of doing this is very illegal in some countries. Yes. hence the name