Horse face loaches can grow up to eight inches so a fairly large tank would be needed for a school of adults. They are peaceful fish, however they will be aggressive towards there own kind. If you do get some I would suggest some good hiding places or floating plants for them because they are nocturnal. I have one in my 75 and it burrows in the gravel sometimes I dont see it for weeks at a time. To avoid that you could use large gravel.
Hmmm form a fish profile: "Tank with small grain gravel, plants appreciated. Sand is ideal.They apprecaiate caves if a larger grain gravel is being used." I think it's helpful!
BTW, they don't need to be kept in school!
G'luck!