Will upgrading the tank reduce the aggression in my tank?

Hello, I currently have a 75 gallon tank that houses a 4 year old Jack Dempsey and a 4 year old firemouth cichlid along with a year old blue acara. I’ve never seen much aggression in my my tank except this past month. The firemouth has gone berserk and doesn’t want to let the Jack eat or even move from the log and will constantly chase the Jack. From what I observe I have never seen my Jack be the aggressor in situation even with other fish I’ve had in the past. The firemouth and Jack never bother the blue acara. I bought a 180 gallon tank a couple months ago and I finally am about to decorate and fill it up and get it going. Do you think when I eventually add my fish to this tank the aggression will stop? I plan on re homing my firemouth because it’s relentless behavior and the Jack seems a little stressed but I’d like to keep him if the aggression would go away with the bigger tank. I also have an Oscar in quarantine for the new tank as well. Would you give the firemouth a chance? He will still be with the jack for a a few more weeks until the tank is ready for them.

Since there has been no previous issue there is a good chance that the firemouth cichlid is a male and wanting a mate. ANother possibility is that the tank's water conditions have gone bad which will also bring out aggression in a firemouth.

Yes, of course, a larger tank could help. When mixing cichlid species one must always make sure that there is enough room for all to set up territories. Still, if the three you named are the main population, the 75 gallon should be plenty large enough as the recommended size tank for a single firemouth cichlid is 30 gallons.

jaylach said:

Since there has been no previous issue there is a good chance that the firemouth cichlid is a male and wanting a mate. ANother possibility is that the tank's water conditions have gone bad which will also bring out aggression in a firemouth.

Yes, of course, a larger tank could help. When mixing cichlid species one must always make sure that there is enough room for all to set up territories. Still, if the three you named are the main population, the 75 gallon should be plenty large enough as the recommended size tank for a single firemouth cichlid is 30 gallons.

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I had a buddy that had a 120 with nearly 2 dozen African cichlids of various species… he got by doing that by relandscaping every other weekend… so maybe yours need more hiding spaces, or it just time to rearrange some of the furniture

Magnum Man said:

I had a buddy that had a 120 with nearly 2 dozen African cichlids of various species… he got by doing that by relandscaping every other weekend… so maybe yours need more hiding spaces, or it just time to rearrange some of the furniture

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There is a world of difference (literally) between African rift lake cichlids (I am assuming by African you mean these colourful cichlids) and all Central American and South American cichlids. Their maintenance is vastly different.

On the Jack Dempsey:
Compatibility/Temperament: Not a community fish. Best kept individually, or may be kept in a small group of 6 or more in a very large tank. Should not be kept in smaller groups due to their aggressiveness. As the fish matures it becomes increasing more territorially aggressive.

The Firemouth by comparison is a pussycat, but only when provided with the environment it needs:
Compatibility/Temperament: Mildly aggressive, rather peaceful for a cichlid. In its habitat, it can be found in small groups though this is not a true shoaling species. Males establish a territory defined by plants, sticks and branches whether or not they are breeding. Suitable in a small group in a 55g or larger aquarium; other fish must be non-aggressive and can include similar medium peaceful cichlids from Central America (in much larger tanks), medium barbs, larger characins and peaceful substrate fish. Not suitable with small fish. Will become more aggressive when spawning.

Tank size obviously is important, but I doubt you will have a tank really large enough for these two, ever. African rift lake cichlids need a tank full, though not beyond the tank's limits, and with some consideration to the different species, but very generally they are used to living with each other (species) for the most part. There are no Central American cichlids that inhabit the same habitat as another cichlid, so putting two species together needs very carefully thought, and obviously will not work for many of them. The stress caused by having the other species is severe. Aggression is the general reaction, but it is due to the stress impacting the poor fish.

yep, had both types of cichlids in my previous life... just saying, in my buddies case ( extreme ) that his tank had a large amount of rocks & caves, & he was able to keep them from death matches by continually changing the scene, so no one had a "permanent" turf...

I had Fire mouth cichlids before, that were aggressive, by offering equal cave space on opposite sides of my tank ( 55 gallon at the time ) & actually feeding on both ends, they were able to cohabitate, though they still roughed it up a bit if they met in the middle of the tank, but had a safe space to go, if things got too rough... food added to the ends often broke up the fights ( they were more interested in the food , than the fight )

KevDiamond823 said:

Hello, I currently have a 75 gallon tank that houses a 4 year old Jack Dempsey and a 4 year old firemouth cichlid along with a year old blue acara. I’ve never seen much aggression in my my tank except this past month. The firemouth has gone berserk and doesn’t want to let the Jack eat or even move from the log and will constantly chase the Jack. From what I observe I have never seen my Jack be the aggressor in situation even with other fish I’ve had in the past. The firemouth and Jack never bother the blue acara. I bought a 180 gallon tank a couple months ago and I finally am about to decorate and fill it up and get it going. Do you think when I eventually add my fish to this tank the aggression will stop? I plan on re homing my firemouth because it’s relentless behavior and the Jack seems a little stressed but I’d like to keep him if the aggression would go away with the bigger tank. I also have an Oscar in quarantine for the new tank as well. Would you give the firemouth a chance? He will still be with the jack for a a few more weeks until the tank is ready for them.

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Loads of great advice in here already but I just wanted to add - I think the move to a 180 will make things better over all. Personally I think that the Jack Dempseys reputation is much worse than it is deserved - it was one of the first cichlid species in the hobby so likely one of the first aggressive fish people kept and I just think its reputation has been passed through books and profiles rather than when people keep them. Firemouths are an interesting one too as they display very very effectively which can scare a lot of other fish - if you ever see a firemouth front on fully flared out the red throat is huge and the markings on the gill covers look like eyes making them look like a much bigger fish.

Firemouths as a Thoricthys are a bit of a gregarious species so adding a few more Firemouths in the 180 might help your other calm down, focus on the hierachy within that species rather than push it out to other species.

I'm a bit concerned at mixing the Central Americans and South Americans as they are quite different in nature - though often lumped together in the hobby. Souths prefer soft and slightly warmer water, centrals prefer cooler harder water as a starting point. Central American habitats are often quite barren rocky basins or drainage systems where as South American are often dense with plants and roots with sandy bases. South American Cichlids often live around lots of other species at any given time where as the comparative Central American habitat will be made up of fewer species over all.

The behaviour of South and Central Americans is quite different too, Central Americans will flare and 'shout' sooner than South Americans so if they do this to a South American the Central American might only be at a 4 or 5 out of 10 but the South will interpret this as a 8 or 9 out of 10 so the fight happens much faster - a simple study of the jaw shapes shows that there are many more predatory Central Americans vs South Americans so on average a Central would win in a test of strength.

I think one other thing to mention at the moment is that if you just keep a tank of Central or South American cichlids and fill it upto capacity with them you are going to always struggle - even in a 180 I would say 2-3 cichlid species max and then build a community around them with suitable choices like large characins (big disk tetras, headstanders), bigger catfish, plecos and whiptails etc. Or for Central Americans go for big groups of larger Livebearers, Blind Cave Tetras and head to the rift lakes for your catfish so things like Synodontis Multipunctatus or Petricola.

Magnum Man said:

I had a buddy that had a 120 with nearly 2 dozen African cichlids of various species… he got by doing that by relandscaping every other weekend… so maybe yours need more hiding spaces, or it just time to rearrange some of the furniture

Click to expand...

It's been covered a bit already but Malawi and Americans are so different, Malawi cichlids are all mouth brooding cichlids so territory is a different concept to American and African riverine cichlids that will stake out a specific space or area as theirs. Malawi males will take territory that covers their requirements for feeding and the act of breeding where as Americans will take territory to raise huge broods of young - so a couple of different evolutionary triggers going on. Malawi are looking for short term spaces the rest are more long term I suppose. Malawi are also different because the fish we keep are typically the 'prey' level fish of the lake so Mbuna species that are near the bottom of the foodchain are overly aggressive to survive where as Peacocks and Haps are open water swimmers and essentially predatory species of insects and fry or young fish of other species, specifically Mbuna. American and riverine African cichlids don't live in such hostility on a permanent basis so their aggression and territorial instincts only kick in

It must also be remembered that the Jack Dempsey is not the aggressive fish in this case but the victim. The Firemouth is the aggressor.

While I've never kept a Firemouth research shows two primary reasons for a Firemouth to switch to being very aggressive. One is wanting a mate and the other is a change to the worse in water conditions.