depends on the wolf species
you won't find an aimara
common wolfs get around 18'' and are pretty territorial and are usually very aggressive and can't be kept with tank mates and are pretty lazy
gold wolf fish will get around 12''-14'' if i remember right and are one of the most active wolf fish they have been kept with other fish but can be aggressive from what i've been told
rainbow/ red high fin wolfs are said to be more active then common but not as active as golds they will get around 8'' and can also be kept with some tankmates but can also be pretty aggressive