I fall on the side of the debate that it's possible to keep a male-only guppy tank, I have done it during breeding and letting the young males mature, and have some males in a community tank who are fine as well. But there are some conditions you have to meet for it to work;
Provide a lot of dense plant cover. The tank in the photo looks a little open and empty. Some swimming space is good, but there also needs to be areas with a lot of plants for them to explore, to break lines of sight, and for a bullied one to hide in and get some respite. You also have to watch, if you have a couple who are more aggressive, they might need to be rehomed, sadly, or go into a tank with some females. Which isn't ideal when you don't want fry...
So add a lot of plants. Floating plants and some fast growing stem ones like hornwort are good. Even with all that though, you can and will get the occasional male who is highly driven and becomes, for a lack of a better word, a dick. I've had a couple that were like that in my male grow out tank, and taking them to the store was the only solution.
aquariumscience.org
although ive never had any issues using it 
. Total rescape from gravel. My other half wasnt happy i spent anothet £100 with first 3 months...whoops
