Agre
You may think aussie'mans statement is a trifle facetious, or an overstatement but......
Even though they are just juvies, the alpha is telling you the tank is too small for thie group of fish.
Your tank is about the same size as a truck tires rut in the road, not the kind of space you'd ever find Geophagus in.
Whenever an aquarist experiences cichlid aggression in a tank, its the fish explaining the space is not adequate.
I have found 6 ft tanks are usually minimum for Geophagines, although some like Acarichthys need even larger tanks.
I have used a 55 as a grow out tank, but usually move them to a larger tank at 2.5-3", but....
One other factor in Geophagine aggression to consider, is current.
In nature they prefer areas in rivers with riffles, and even rapids
Geos prefer at least medium to strong laminar flow, across the length of a tank.
If they have current to work against, it seems to temper aggression.
Beside normal filtration water movement, I usually place a power head ( wave maker) pushing strong flow across length of the tank to offer some riverine type flow.
Above a power head I add to normal file effluent in riverine cichlid tanks.
Below the normal filter effluent discharge flow.
Below a shot I took in the normal flow of a section of river in Colombia where Geophagus steindachneri is found.
I have kept at least 10 species of Geophines over decades, and never found one, that didn't do best in at least 6 ft tanks, without what many aquarists would consider "too much" flow.
And agree with neutrino, large shoals are very important to the dynamic of how they interact, peacefully, or not.
But in a rank as small as a 55 ........
