It's certainly possible- but i was keeping 4 of these fish in a 20 gallon high, before i moved them to their new 60 gallon home and have had no problems with aggression.
These are small fish of course 1.5 inch females (i beleive) and the single 2 inch male.
Their aggression is negligable compared the other fish in the 60 gallon, as they are all bigger.
In my 60 gallon i currently have -
2 Pseudo Luwalas
2 Pseudo Zebras
4 Pseudo Demosani (1 male 3 female- i think)
2 Jewel Cichlids (mated pair i beleive)
2 Kennyi (Pseudo Lombordoi)
1 Yellow lab
1 Golden Mystery Snail
Largest is one of the kennyi's at about 2.25 inches.
Please forgive my mixing scientific and common names as i'm tired and don't feel like looking them all up atm
None of my fish is over 2 inches at this point and they may certainly outgrow their current behaviour, but my crop of Pseudo Demosani are not at all aggressive.
I am also using a heavily planted tank, so the behaviour may not be normal! However, i find the fish were far more aggressive without plants. If they have a place to hide, there are no real problems. I will be curious to see if this is the case as they get bigger