I have recently purchased a new 40 [ uk ] Gallon juwel aquarium, which i have gradually moved my 2 black anglefish into, along with 7 black tetras and 3 platys. Eventually i will add the remaining 4 black tetras and 3 green tiger barbs from my smaller tank. Up until the move the angles were very placid, but recently they have become aggressive towards each other, i.e, locking mouths and biting each other on the side, causing obvios damage, i am not sure if this is just mating behaviour or serious aggression 
Also i was wondering what other types of fish i could add that wont outgrow the tank, and how many would be a safe number ?
Also i was wondering what other types of fish i could add that wont outgrow the tank, and how many would be a safe number ?
