Angelfish showing aggression?

[AuroraFly]

My angelfish has been chasing the others around the tank lately. It's a 55 gallon with sand substrate, planted with Amazon swords and Java fern. Water params are good, 0 ammonia, 0 nitrite, 10 nitrate. Temp is 78F, and I do 25% water changes weekly. Any idea why it's acting up?

[MrCockroach]

Aggression in angelfish can stem from territorial behavior, especially if they're mature. How old is the aggressive one? Also, what's the male to female ratio? Sometimes adding more plants or rearranging decor can break up established territories.

[jolux]

Mine did the same thing until I added floating plants like frogbit. Gave the others places to hide. Maybe try that? Also, what kinda filter you running? Could be flow stress.

[coralone]

My angelfish has been chasing the others around the tank lately. It's a 55 gallon with sand substrate, planted with Amazon swords and Java fern. Water params are good, 0 ammonia, 0 nitrite, 10 nitrate. Temp is 78F, and I do 25% water changes weekly. Any idea why it's acting up?

Sounds like classic dominance vibes. How many angels you got in there? Might be time to rehome the bully or add more hiding spots.

[AuroraFly]

Thanks for the suggestions. There are 4 angelfish total, all around 8 months old. I'll try rearranging the decor and adding more plants. The filter is a Fluval 307, flow seems moderate.

[MrCockroach]

At 8 months, they're likely hitting sexual maturity. The aggression could be breeding behavior. If you don't have a pair, the dominant one might be asserting itself. Monitor for pairing off or egg-laying.

[jolux]

Yeah, mine chilled out after a bit. Maybe just a phase? Also, what's your feeding routine? Hungry fish get cranky.

[coralone]

Aggression in angelfish can stem from territorial behavior, especially if they're mature. How old is the aggressive one? Also, what's the male to female ratio? Sometimes adding more plants or rearranging decor can break up established territories.

Totally agree. Also, sand substrate can make 'em more territorial since they like to claim spots. Ever tried a darker background? Might cut the stress.