Today I noticed a new behavior in the fish. Normally all of the comets, common goldfish, and shubunkins swim together in a peaceful school. There are about 40 currently, I would guess.
I saw a group of 4 goldfish, swimming tightly together (not as a normal school, but touching each other), chasing/attacking another individual fish. They were pushing the fish around. It was usually an orange fish with black fins, but the scales around its belly became completely white. Then I saw a completely different group of 3-4 fish chasing yet another fish.
- I did recently run out of fish food, so they lost out on food for two days, but I was able to order more and they're back to being fed, so saw this behavior after they received food for two days.
- I recently added 50 new plants to the pond, and an algae bloom has appeared, possibly due to adding lots of fertilizer in the pond plants pots.
All of the fish involved are quite small, about 1" to 1.5" fish.
Why might they be attacking each other?