Angelfish - strage behavior at night

[DallasFish]

I have three angelfish in my freshwater tank, all added at the same time and with a body size about that of a silver dollar.

I noticed last night after the lights were mostly off that one angel was chasing another all around the tank, ramming into it. When I turned the light on, the behavior stopped, and everyone swam peacefully. I turned the light back off, and within a few minutes it started again.

Any idea what is going on? Do I need to move one or the other of the two involved out of the tank? Thanks for your help!

 

[Taelen]

People who know much more than I will tell you they are very territorial. Not sure about the lights though. I find their behaviour difficult to predict based on the ones I have owned.

 

[bs6749]

I've got 15 angelfish in a 29 gallon tank and they have spawned 3 times for me so far. They don't chase each other as you have described and they don't even act as hostile towards each other when breeding as my GBR's were. IMO they aren't "very territorial" but they seem to have their own spots that they protect more with showing fins than chasing and biting. Maybe there is breeding activity going to take place soon in your tank and there is an extra male that keeps tryinig to join the pair. Maybe add 1-2 more angels and see what happens. This would help to spread out the aggression.