A cichlid tank has an established pecking order, with the dominant cichlid at the top. If one of the other fish crosses him -- literally -- you can expect trouble in your tank. Changing up your tank environment or putting the dominant cichlid in time-out can change his ways.
Overstock your tank slightly. The stock of a tank is usually expressed as a percentage and depends on what type of fish you have and the size of tank you have. Usually it's a good idea to keep a tank stocked at 100 percent or lower, but at 115 or 125 percent, the dominant cichlid will encounter a slight problem when he chases after other fish: they become lost in the crowd, so he's forced to abandon the chase. Don't go by the simplistic 1-gallon-per-inch-of-fish rule. Instead, use one of the many online tank stock calculators.
Give your tank a makeover. Dominant cichlids stake out certain territories. If a fish dares enter that area, he's quickly chased out and sometimes physically disciplined. Switching around the placement of your decorations and larger plants changes up the territories, and the dominant cichlid will usually no longer aggressively patrol the same area. He will, of course, find different areas in time, but the makeover reduces aggression temporarily. Don't change up your tank any more than every two months or you may stress out your fish.
Block the dominant cichlid's line of sight. Forget about filling your tank with tiny terracotta cups or small skulls. Go with wide and tall decorations, like castles, large plants and logs. A tank that's plentiful in larger decorations blocks the dominant cichlid's line of sight, so he more easily loses the fish he's going after.
Add more hiding spots. Don't completely abandon your smaller decorations in favor of larger ones. Smaller caves and hiding spots can help fish escape the dominant cichlid.
Add about 6 schooling fish, such as silver dollars or tiger barbs, to distract the dominant cichlid. These fast fish school together and dart out of the way when a cichlid goes after them, freeing your other fish from being constant targets of the dominating cichlid. As long as you provide plenty of plants and hiding spots, the schooling fish shouldn't suffer any injuries.
Put your dominant cichlid in time-out. Placing the high and mighty in a separate tank for a week can do wonders for your aggression problems. All the other fish move on up the line, basically establishing new positions within the tank. After you place the once dominant cichlid back in his tank, he'll find that he's no longer the top fish.
- Keep an eye on your tank for the first few weeks if you overstock it. Make sure ammonia and nitrite levels remain at 0 and nitrate levels do not surpass 40 parts per million. Use a water test available from pet stores.
- Feed your fish regularly, per the directions on the food label. If you infrequently feed your cichlids, they may all act more aggressively, but especially the dominant one.
- Make sure the time-out tank has a filter and heater and is cycled. If it's not cycled, take filter media from your established tank and place it in the filter of the time-out tank.
Located in Pittsburgh, Chris Miksen has been writing instructional articles on a wide range of topics for online publications since 2007. He currently owns and operates a vending business. Miksen has written a variety of technical and business articles throughout his writing career. He studied journalism at the Community College of Allegheny County.