[SWHouston]

I will not argue that Training and Neutering are established methods to deal with a problem like this, but, it certainly would have been more controllable if you had created a stricter Pack Pecking Order as you accumulated your animals. This can be extremely difficult for some people/owners, in that they try to "'treat" all the Dogs on an equal basis. That is not the way things work in a well functioning Pack regardless of the gender mix, or lack of in your case.

The problem that you are experiencing is that your little Piranha is desperately struggling for the Alpha position, which he should have given his tenure with you, in the only way he knows how, and you are not supporting that.