Tropical fish clumping in corners instead of swimming freely

I decided to build a secret underwater aquarium and spawn a bunch of tropical fish. I noticed that I had too much coral when the fish started to get stuck in one spot so i used the splash potion of instant damage to kill them all. The game did freeze and I had to restart it. After reconstructing the aquarium, i spawned the fishes but less than i had before. I noticed how they were in clumps instead of swimming around freely like they did before (the aquarium was enclosed so they were clumping in certain corners. I user the command to kill all entities and decided to make some openings so that way they won't clump anymore. After this, some of the fish were swimming in one position instead of moving freely. I've seen some of the fish clumping but in smaller groups. Is there a possible way to fix this bug? Thank you for reading this and god day.
Kianna Harris
CAPQueen69