Too close to call in my mbuna tank. Who's 'tough' depends on who's dealing with who. This is only a mildly agressive 6' tank, with acei, estherae, yellow labs, c. afra, mainganos, lab mbambas and lwanda peacocks. With the exception of the yellow labs, right now the dominant male of
any one of those species (including the lwanda) can take on an attitude and rule for awhile. One of the ones that has been standing out of late is the acei ('cause he's gotten so BIG), but the terror is usually directed towards conspecific subdominant males...
(PS: I actually thought of entering this shot in the montthly photo contest, but since you can see more than just the acei I figured it would be disqualified as a 'tank shot'.)