How many male guppys do you have?
My main advice with keeping an all-male guppy tank is;
a. The more males the better as the more dispersed any agression will be amoungst them the larger the group you go for- i would aim to have at the bare minimum 5males, although more would be better. Up until recently, i had an all-male guppy tank of 18males and it worked pretty well.
b. Understock the tank and provide plenty of planting- planting makes good hiding/retreat places for guppys, and by under-stocking the tank you will help prevent the overal stress levels of the fish, the less you crowd the tank the better.
c. Only go for standard short tailed guppys- avoid the fancy types. Look for males which are large in size and have a good sturdy build to their body- fancier types of male guppys with longer tails like delta tailed guppys tend to be weaker and more prone to being picked on.
d. Provide plenty of filtration, its good to have two filters in the tank, however have the filter current turned down to medium-to-weak strength current as a strong current in the tank can tire male guppys out if they are not used to it, and a current which is too strong can cause split tails in the fancier types of male guppys.
Its normal for male guppys to try and mate with each other in all-male groups, its partly because they are very highly sexed fish, but more than anything it is not anything to do with love but rather it is an act of dominance over the weaker male.
Overal, getting all-male groups of guppys to work well can be a difficult buisness, you may have to swap different males quite a few times before you come up with a group that works.
If you go for a mixed gender groups, you need to have at least 2-3females per male minimum, preferably more females if you can. You will get lots of fry though, particularly if the 11 guppys you have in your sig are all males, you'll need at least 22 female guppys, and considering that each can produce over 30fry a month, you may find yourself quickly overstocked with guppy fry and desperate to find a solution as what to do with them all etc. Personally i would have no more than 15guppys in a 30gal.
By the time I realised what the problem was it was too late. I added some females with him instead and that seems better but as my sig says I did have some fry get through 
He's mellowed a bit now (getting old?!) and doesn't seem so bothered about the other males but maybe this is because there are other females too...
