Hi, so I have a 10 gallon aquarium tank in my bedroom. Before I bought any fish it was cycled for 31 days. So with pride I set out to buy my first Blackmoor fish, I chose one in particular because he seemed quite quiet and minding his own business (even though the pet shop tank he was in was over crowded). He's been in my tank for another month and has been doing really well by himself, every 5 days I do a 50% water change and the tank is cycled 24/7. Water tests are showing almost zero ammonia and PH levels are 6.5/7 and the rest coming up normal. No disease symptoms (had previously had fish who came in with white spot about a year ago)

Anyway, today I decided he's settled in really well and was time to get him a friend. So I went to the pet shop and bought a telescope goldfish. I figured it would be a good match as they are both the same size (maybe an inch big) and they swim similarly so they won't be unfair when it comes to food.

So I put him in and now the blackmoor seems to be chasing him around the tank and nibbling his tail. I've fed them to try and grow the bond but the black still is chasing him. He doesn't seem to be doing any damage and I'm wondering if there's a way I can stop this from happening? Is it over the territory? Food? Or just dominance?

Any help would be appreciated :)

I am aware when they grow a little they will need a bigger tank but for now as they seem so small I figured it would be good to use my old one.

Thanks