Neapolitan Mastiff with Mini Dachshund

So a few days ago my fiance and I brought home a 17 week old female Neapolitan Mastiff (55 lbs). We already have a 6 Y/O male Mini Dachshund who is the definition of a lap dog (6 lbs).

I'm a fulltime Firefighter/Emt and my fiance is a Paramedic. Both of us have rotating day/nightshifts and sometimes our work schedules mirror each other times they are oppisite.

The therory behind us getting the Neo was two fold. When I'm at work overnight and my fiance is home alone she wanted a larger "guard" dog to feel more safe. The other half is on the nights/days when we both work, the dachshund would not be alone in the house and have some companionship. The neo seemed to fit that need perfect.

They are both great dogs and we were plesently suprised with the Neos mellow temperment as she is very well behaved for a puppy. The only problem is when they are together...

The Neo is very playfulat times, given she is still a puppy, and attempts to play with the Dachshund constantly. The dachshund is either very aggresive or withdrawn toward the Neo. When the mini is agressive or barks, the Neo just sees that as playing and continues. I'm finding it hard to keep the Neo controlled with a stern vioce and some restraint when she tries to play with the mini we don't want him to get hurt. I know this is only going to get harder as she grows larger.

At the same time I don't want to discourage the Neo from playing with all other dogs her size when we try to socialize her because i don't want her to be aggressive toward other dogs as the mini always has been.

It might not have been the best choice in breed already having the mini, but we are not sure given its only been a few days wuth them together. We are crate training the Neo and she does very well with that. Was our thought of the Neo a compation for the mini far fetched?

Looking for advice PLEASE...

Wow - tough call! As you're already aware, Dachshunds are fearless, so even when your Neapolitan Mastiff has grown - your Dachshund - despite his small size - will still be fearless! Generally Dachshunds do well with other dogs - as long as they've been raised with them and / or properly socialized. It's only been a few days - so this is definitely something new she'll have to get used to.

Keep in mind that not only is there a "surprise!!" - new member to the family - I bet your Neapolitan Mastiff is getting loads of attention - attention that used to belong all to your Dachshund. I can see a lot of jealousy going on here - so be sure to show just as much attention and love to #1 while of course keeping the upper hand : ) Adult socialization is still an option for your Dachshund, so since this breed generally gets along very well with other family pets, it will just take time for this adjustment. Best of luck to you!