Male guppies bullying and nipping at Mollies

I have a 10 gallon aquarium I set up for my 7yr old daughter to introduce her to fish...We got 3 male guppies and a couple of Mollies (fire-something, I can't remember) and the guppy males, after a few days, began harassing the mollies, eventually nipping the larger one to death after about a month...the remaining molly is running and hiding for its life...I went and got 4 Zebra Danios at the recommendation of the pet store. I thought about getting females, but didn't want all the breeding of guppies. Will my Danios be OK? And would it be safe to put a Cory or two in as well?

 

Are the mollies female? Guppies and mollies can cross breed, they maybe harassing trying to mate.

 

Honestly, I am not sure...but they are REALLY after the remaining Molly now and have left the Danios alone...I feel bad for the fish and I don't have another tank to put it in...I am tempted to take it back to the store for an exchange before I have to return a corpse!!!

Maybe not having any female guppies has put the three male guppies on a testosterone rampage!!! lol

 

I have had all male guppies with no problems, but other people have had issues. However if the molly is female, it would be just like having 3 male guppies and one female guppy. You could try returningv the molly and see what happens.

Another issue could be overcrowding. Mollies get to big and active for a 10gal, and with the guppies and now danios( which also need a larger tank) the tank is overstocked, crowded fish can get aggressive.

 

Lexi, thanks for your advice, I really appreciate it...Do you really think that 4 Danios and 3 guppies is overcrowding for a 10g? I figure 8 inches for the Danios at maturity and 4.5 inches for the guppies, which should only put me at a 12.5 inches of fish...Anyway, could it be a territorial issue with the guppies, since they were the first set of fish in the tank?

 

The danios need a larger tank because of their activity level, they are crazy hyper fish and need a bit of room to stretch their fins. While you may not be over stocked bioload wise, space wise they are a bit crowded.

Guppies don't tend to be territorial fish, males are pretty much only programed to breed. Normally in favorable tank conditions, they should only get aggressive when there is a female to fight over/ harrass, but not enough females to go around (3 females to 1 male).

 

So most likely the Mollies are/were females and the Guppy males are just attempting to breed...thanks again for help...

 

I would have to agree, sounds like a breeding thing to me.

I have a tank full of male guppies and while there is the occasional spat they are not at each other all the time.

Also those Danios will appreciate a larger tank as they can be a VERY active fish, thou quite enjoyable to watch.