I agree with Gourami Swami
As juvies salvini can be quite shy, and retiring, but don't let this fool you into a a false sense of what is to come. Once they hit maturity, I would put the Trichromis aggression level at 9.9 (one of the most aggressive Central American cichlids, pound per pound) compared to a
GT at about a 3 or 4 depending on the individual.
I find the common name G Terror to be quite misleading by Central American cichlid aggression standards.
I also like GS's idea of more than 2 or at least a bunch of non-cichlid tank mates.
Salvini are from the Atlantic coast of Mexico, and in nature would be surrounded by large shoals of live bearers (although Astyanax tetras are also quite common).
GTs are from west and north of the Andes in South America, and would share habitat with a higher concentration of tetras (Colombian types come to mind)
Either cichlid will set up territorial boundaries in either size tank as they mature, and spend most time in the lower half of the tanks. Dither fish such as tetras or live bearers large enough to not be eaten, would create interest in the upper areas, and provide a security blanket of sorts to make the cichlids less wary and come out more.
Loaches on the other hand, being ground huggers, may become a territorial threat, especially in the eyes of the salvini.