Can Ammonia Levels Trigger Aggression In Chiclids?

[pcam86]

Hi, i currently have a 180 litre tank with 3 snails and 5 small angelfish. The angelfish have recently started getting aggressive towards each other and i was just wondering if thats due to "them" or if ammonia in the water stats can have any effect on how they act?

 

[WILDER]

Yes how high is the reading, as it can burn and irratate there skin, wouldn't actually put me in a good mood.