Fish aggression ratings

[SalviniCichlidFan]

Mine is the king cichlid. He himself is harmless, but he knows how to run a tank. His secret is to be paired with my convict as his enforcer lol. He butts heads with the leporinus, which as far as I’m concerned means he’s got balls.

lol BPs have the balls of a red devil but with no actual weapons except their balls. My BP concerns himself with fish-human interactions unlike the other fish which compete for dominance amongst themselves. Speaking of your BP pairing with your convict, my cichlids have made alliances as well. Rather unlikely ones in fact. My fire mouth allied himself with my OB peacock.

 

[Deadeye]

lol BPs have the balls of a red devil but with no actual weapons except their balls. My BP concerns himself with fish-human interactions unlike the other fish which compete for dominance amongst themselves. Speaking of your BP pairing with your convict, my cichlids have made alliances as well. Rather unlikely ones in fact. My fire mouth allied himself with my OB peacock.

My parrot and con are a mated pair. No fertile eggs though.
My leporinus and Jack have an alliance though, built out of hatred for the other two lol.

 

[duanes]

The determination of an aggression scale has more to do with tank size, and territoriality than fish size.
In a 2 to 4 ft tank, a 3" JD or FM or other cichlid might kill every other fish in the tank within a short time.
In a 6 ft tank either may be only aggressive to other similar looking cichlids.
In a larger space (8ft +) they may be totally harmless.
A friend had a 10" FM in a 300 gal tank, and a number of other largish cichlids, with no aggression at all. But..
I have tried to keep 12" Paratilapia together in a 400 gallon kiddy pool/pond, where they killed each other.


Or where I put a dozen 7" Panamanian GTs in a 6 ft 185 gal, and the dominant male killed all others except the 3 females he consorted with, but left all non-cichlids unharmed
..

 

[C. Breeze]

I have 50ish HRP and Cutteri growouts in a 55 gallon tank with no aggression.

I have 5 HRP growouts in a 10 gallon fasting to ship and it’s a war zone….

Your aggressive Fish are going to be basically predatory (interpreted as aggression) or be so situationally aggressive that your algorithms are going to need to be quite complex…

 

[SalviniCichlidFan]

The determination of an aggression scale has more to do with tank size, and territoriality than fish size.
In a 2 to 4 ft tank, a 3" JD or FM or other cichlid might kill every other fish in the tank within a short time.
In a 6 ft tank either may be only aggressive to other similar looking cichlids.
In a larger space (8ft +) they may be totally harmless.
A friend had a 10" FM in a 300 gal tank, and a number of other largish cichlids, with no aggression at all. But..
I have tried to keep 12" Paratilapia together in a 400 gallon kiddy pool/pond, where they killed each other.
View attachment 1468854

Or where I put a dozen 7" Panamanian GTs in a 6 ft 185 gal, and the dominant male killed all others except the 3 females he consorted with, but left all non-cichlids unharmed
.View attachment 1468855.

Thanks for the info Duanes! I can see this being true as the native species in my area, bluegill sunfish, act like schooling fish in the local ponds and lakes, but in a fish tank they become hyper-aggressive. I'm probably going to add a tank size variable which influences user input of aggression.

 

[Deadeye]

The determination of an aggression scale has more to do with tank size, and territoriality than fish size.
In a 2 to 4 ft tank, a 3" JD or FM or other cichlid might kill every other fish in the tank within a short time.
In a 6 ft tank either may be only aggressive to other similar looking cichlids.
In a larger space (8ft +) they may be totally harmless.
A friend had a 10" FM in a 300 gal tank, and a number of other largish cichlids, with no aggression at all. But..
I have tried to keep 12" Paratilapia together in a 400 gallon kiddy pool/pond, where they killed each other.
View attachment 1468854

Or where I put a dozen 7" Panamanian GTs in a 6 ft 185 gal, and the dominant male killed all others except the 3 females he consorted with, but left all non-cichlids unharmed
.View attachment 1468855.

Well said! If fish in the wild were as mean as in the tanks we put them in, there wouldn’t be any left...
Is the FM you mentioned firemouth? Those can get 10 inches?!

 

[duanes]

Yes FM is fire mouth.
Takes them a while to get there, but yes, 10".
I believe the reason we don't often see full potential FMs in average aquariums, is they are kept in too small tanks, where water quality is quickly degraded, and they stunt from less than optimum conditions like high nitrate, and other deleterious mineral and hormonal buildups.
Same thing with JDs.
In nature they often live in Cenotes where there is constant 100% water change every hour, and nitrates are 0.00ppm, and where a single alpha pair might commanders an area of about 250 gallons. Like the pair I photographed below, in Cristalino Cenote.



They would chase all other JDs out of an area of about 8 square ft, allowing only the shoals of live bearers, they watched to determine threat of danger to stay (although they often preyed upon the live bearer fry.
The alpha JDs above average 10"-12"

 

[jjohnwm]

Yeah, lots of variables involved here. Another big one is age/size of fish. Plenty of cichlids and some other fish seem okay as youngsters, then become...either gradually or suddenly...homicidal once they hit some obscure growth milestone.

It's always entertaining to read some of those threads:

Aquarist #1: "Yeah, I bought a baby XYZ Psycho-Assassin Killer Cichlid and put him in my 10-gallon tank with some guppies. I don't know why these fish have such a bad rap; mine is best buddies with the guppies, and likes to school with them!"

Aquarist #2: "That's amazing! How long has he been in there with them?"

Aquarist #1: Checks the time on his phone...

 

[SalviniCichlidFan]

Yes FM is fire mouth.
Takes them a while to get there, but yes, 10".
I believe the reason we don't often see full potential FMs in average aquariums, is they are kept in too small tanks, where water quality is quickly degraded, and they stunt from less than optimum conditions like high nitrate, and other deleterious mineral and hormonal buildups.
Same thing with JDs.
In nature they often live in Cenotes where there is constant 100% water change every hour, and nitrates are 0.00ppm, and where a single alpha pair might commanders an area of about 250 gallons. Like the pair I photographed below, in Cristalino Cenote.
View attachment 1468862
View attachment 1468863
View attachment 1468864
They would chase all other JDs out of an area of about 8 square ft, allowing only the shoals of live bearers, they watched to determine threat of danger to stay (although they often preyed upon the live bearer fry.
The alpha JDs above average 10"-12"

Cool! You live near Cenotes? Im trying to make a Cenote environment in my cichlid tank!

 

[SalviniCichlidFan]

Yeah, lots of variables involved here. Another big one is age/size of fish. Plenty of cichlids and some other fish seem okay as youngsters, then become...either gradually or suddenly...homicidal once they hit some obscure growth milestone.

It's always entertaining to read some of those threads:

Aquarist #1: "Yeah, I bought a baby XYZ Psycho-Assassin Killer Cichlid and put him in my 10-gallon tank with some guppies. I don't know why these fish have such a bad rap; mine is best buddies with the guppies, and likes to school with them!"

Aquarist #2: "That's amazing! How long has he been in there with them?"

Aquarist #1: Checks the time on his phone...

at least it's a constant food supply... lol