We have two goldfish who are in a 10 gallon tank. the one who is orange and white in the attached video seems to have red gills. Does anybody know if what we're looking at is normal or is this something that we should be concerned about?

We have the water on a filter regular cycle through ammo trips and carbon bits. I plan to refresh the water once a week about 20%.

The gold and orange fish does seem to exhibit some aggressive behavior towards the other. I know that that may be causing some stress and I'm concerned about the orange and white one.

Thoughts welcome.