Can I keep a group of all male mollies? No females?

It might not work to have only male mollies

When you see them at a store, there are usually males and females together in a small tank, and this keeps a balance for the group not to harass each other. If you try to separate them into just males, you stand the big chance of them fighting, harassing each other, and nipping the fins. If a pecking order gets established, and some hide away and don't mix with the others, they could survive, if you don't mind the constant fighting. I took some home and found this happened immediately, so had to go back and buy many females to counter this.

If you are worried about babies, just leave them alone, fry will be born and then eaten by the adults pretty fast. Maybe one or two might hide and survive until they are 1 -2 months old. But you have to have a well-planted tank with lots of places for them to hide. I was trying to save the fry, and saw 3 being eaten right away. This is a safer bet than keeping only males. Females are usually pregnant, but they are milder and will keep the aggressive males busy.

Graceful and Neonflux: "I do not want to deal with babies! I'm wondering if it's OK to keep a group of all males."

Quite true, Cspencer83, re Molly behavior

I have been watching the Mollies and their interaction, and the males are very aggressive, especially if you don't have any, or enough, females in there. There is an alpha male and an alpha female, which dominate the others. You want to keep the aggressiveness down as much as possible, because you don't need fin-nipping and growly behavior. I let the Orange Sailfin Male do his thing with the females, though the very beautiful Green one is shy, and doesn't get much of a chance to chase the females around. He spends most of his time avoiding the Orange one. If you wish to breed a certain shy male with a female, you have to separate them so the chosen pair will mate. If not, then having lots of females will make them all settle down, and be more agreeable and mild. At least 3 females per male or better...

When female Mollies are in heat...

When are they NOT in heat??? Maybe when delivering the babies? Males after them ALL the time!!!

I know my 20G is too small for much, but I do have 6 Mollies, 3" and 1.5", 4 females, 2 males. (was 6 females, but took 2 out). Two had babies, so were put into another tank. I can see that the Alpha male, Sailfin GoldDust/orange with green sparkly fins, who is extremely aggressive, is the head fish. He is the dominant one, keeps the other one hiding. So I probably will get many orange fish from him, as the other one tries to go to a female, and is chased away by the orange male. He is a handsome one, so no problems there. But having bred birds once upon a time, I can tell a dominant one for sure.

I think if I had a larger tank, there wouldn't be any sparring, but for a small tank, you have to live with the extra cleaning and heavy bioload to keep the water sparkling. It is clear now, and all the 10G tanks, too. Never had a problem with the 10G tanks, once I learned what cycling is, and how to do it. Thank you for all the tips, and I am getting better at it now.
:lol:

I know what you mean!

When my female is about to deliver, I know she gives a scent which drives the males nuts, so I remove her beforehand, and thus she doesn't have to deal with that besides the birthing. It is stressful enough with the delivering process. I have a 10G tank for her to get into the process, and no others around to harass her and the new babies. It also makes her removal easier -- have a tank separation divider to keep babies out and give her a few days to recover. I move her about 5 days to a week before.

Despite having 4 females give birth recently, and seeing them in the tank right in front of me, I have yet to actually see a baby being born. Not like the videos on this, my female is hyper, running up and down the corner at the edge, eating everything in sight. She is not still at all. Sometimes pushes her bottom up against a shell to help it along. Just thought I'd mention this, none of them have been quiet and not moving. They seem anxious to get the babies on their way.
:roll: