Firstly, if anyone else has any other advice please add it 
Dealing with aggression is a headache for us all at some point, these are just a few things I have personally tried that have worked.
Tank re-arranging:
a) Removing the aggressor to a seperate tank for a day or so, re-arranging the tank then adding the aggressor back in. It does work, but sometimes you have to try quite a few times before the aggressor calms down.
b) Decor: are the fish squabbling over a particular cave, ornament or plant? if so remove it, so there is nothing to fight over. Change it for something else.
c) Swimming space and chill out space. My tanks have decor, plants etc at either end leaving the middle clear, if a tussle does occur the fish can sulk at either end of the tank well away from each other. Plus having the decor at both ends allows the fish to have thier own territories away from each other.
d) Try raising decor, use really tall plastic plants, tall bogwood so there are different levels of hiding places not just all on the bottom.
Feeding:
a) Feed less as more hungry cichlids will spend time mooching for food than attacking their tank mates, but dont underfeed so they are starving.
b) Food they have to work for. Veggies, prawns etc. I sometimes hide chopped prawns around the tank, stuffed into holes in rock or in plastic plants making the fish "work" for their food, keeping them busy. Or with veggies & cucumber instead of securing it all, secure a couple of peices and leave some floating for the fish to chase, again keeping them busy.
c) add some pest snails, I watch my cichlids quite reguarly hunt out snails, rooting them out from the gravel.
d) Cichlids love food and as most of us see at feeding time they rush to the glass waiting, keeping them slightly hungry is a bonus, because if you see a squabble starting and you go to the tank and they are hungry, the squabble is usually forgotten the moment they see you as they think food is comming. If they start to squabble again once you have moved away just add a tiny amount of food or some food to chase (point b) so they totally forget about it.
Dither fish: Sometimes having dither fish as "targets" helps keep cichlids occupied, however I found particularly with my severums that the giant danio's I had bothered them and caused problems. I watched my one sev watching the danios swim up and down, he was constantly moving his eyes watching them and as soon as the other sev came near him he went for it. Once I removed the danios he totally realaxed and pair up with the other sev lol. Just watch your tank and observe what triggers an attack if you have dithers, it maybe the dithers constant movement annoying a cichlid that just wants to hang about where he is.
red tailed black shark. Lots of these get re-homed because they are too aggressive for community tanks, I have one in my cichlid tank and he is a godsend (pain too) if any flaring starts he is usually straight in the middle of the action (think he has a deathwish lol) and the squabbling cichlids usually then give chase to the shark, who is fast enough to escape and hide, but unlike dithers he will "chill out".
Whether this true or not I am not sure, but it seems to keep my guys calm. I moved my tv next to my tank as we were decorating (which hasnt been done yet) and I find myself watching the fish watch the tv, obviously the changing screen gets their attention not the actual program, but they do seem to like spongebob squarepants
Just like to state that all the above is not a written guarantee to have a calm cichlid tank as they are smart fish and have their own personalities, its just some things I have done that have worked for me.
Dealing with aggression is a headache for us all at some point, these are just a few things I have personally tried that have worked.
Tank re-arranging:
a) Removing the aggressor to a seperate tank for a day or so, re-arranging the tank then adding the aggressor back in. It does work, but sometimes you have to try quite a few times before the aggressor calms down.
b) Decor: are the fish squabbling over a particular cave, ornament or plant? if so remove it, so there is nothing to fight over. Change it for something else.
c) Swimming space and chill out space. My tanks have decor, plants etc at either end leaving the middle clear, if a tussle does occur the fish can sulk at either end of the tank well away from each other. Plus having the decor at both ends allows the fish to have thier own territories away from each other.
d) Try raising decor, use really tall plastic plants, tall bogwood so there are different levels of hiding places not just all on the bottom.
Feeding:
a) Feed less as more hungry cichlids will spend time mooching for food than attacking their tank mates, but dont underfeed so they are starving.
b) Food they have to work for. Veggies, prawns etc. I sometimes hide chopped prawns around the tank, stuffed into holes in rock or in plastic plants making the fish "work" for their food, keeping them busy. Or with veggies & cucumber instead of securing it all, secure a couple of peices and leave some floating for the fish to chase, again keeping them busy.
c) add some pest snails, I watch my cichlids quite reguarly hunt out snails, rooting them out from the gravel.
d) Cichlids love food and as most of us see at feeding time they rush to the glass waiting, keeping them slightly hungry is a bonus, because if you see a squabble starting and you go to the tank and they are hungry, the squabble is usually forgotten the moment they see you as they think food is comming. If they start to squabble again once you have moved away just add a tiny amount of food or some food to chase (point b) so they totally forget about it.
Dither fish: Sometimes having dither fish as "targets" helps keep cichlids occupied, however I found particularly with my severums that the giant danio's I had bothered them and caused problems. I watched my one sev watching the danios swim up and down, he was constantly moving his eyes watching them and as soon as the other sev came near him he went for it. Once I removed the danios he totally realaxed and pair up with the other sev lol. Just watch your tank and observe what triggers an attack if you have dithers, it maybe the dithers constant movement annoying a cichlid that just wants to hang about where he is.
red tailed black shark. Lots of these get re-homed because they are too aggressive for community tanks, I have one in my cichlid tank and he is a godsend (pain too) if any flaring starts he is usually straight in the middle of the action (think he has a deathwish lol) and the squabbling cichlids usually then give chase to the shark, who is fast enough to escape and hide, but unlike dithers he will "chill out".
Whether this true or not I am not sure, but it seems to keep my guys calm. I moved my tv next to my tank as we were decorating (which hasnt been done yet) and I find myself watching the fish watch the tv, obviously the changing screen gets their attention not the actual program, but they do seem to like spongebob squarepants
Just like to state that all the above is not a written guarantee to have a calm cichlid tank as they are smart fish and have their own personalities, its just some things I have done that have worked for me.
