oh no!

So my girlfriend forgot to mention to me yesterday that whilst i was sleeping after my nightshift that she let cleo out of the cage to play with nico....but after a minute or so cleo grabbed his leg and flubg him across the room and he started showing his teeth. Cleo was never a bad dog just with house moving probs theres isnt many places to walk and my gf taken ill cleo does not get get walked as much as she shouldand we feel bad for that .... and maybe this is the reason shes prob snappin as when she is in her cage nico runs riot around it barking growling and snappin at her .... has noco brought thus upon himself

no expert here but i think youll find that a bitch will usually be dominant over a male
sounds like cleo put this little rascal in his place, when hes older he should show her more respect but until he learns i wouldnt trust them together unsupervised
hope he wasnt hurt
sounds like hes got a lot of pent up energy there , if you cant take him out then play games indoors with him to tire him out

I think Kathy is right, sounds like frustration and putting Nico in his place.

Defo putting him in his place, never had 2 but this is what it sounds like, not a bad thing but needs to be monitored

So, is Cleo in the cage most of the time? As well as not being walked?

Why did you get another pup if you don't have anywhere to walk him or any time?
Definitely sounds like frustration which will only get worse as he grows especially when he sexually matures, he needs mental and physical exercise to keep him calm not cage rest.

Small walks a day are better than nothing. If you dnt sort the problem it will only get worse and will cause your dog severe behavioural problems .

We let nico run about the house and play with him for hours on end and cleo gets her walks twice a day

But is Cleo in her crate for the rest of the time? That's an awful long time for her to be locked up even with two hours a day walking.

How old is Nico? Why isn't he being walked? Running around the house doesn't count, he needs sights, sounds and socialization!! And second the crate question? Is she in the crate whenever not being walked?