I have a 7 year old male Leonberger and a 11 month old male newfie.  The newfie was introduced to my older dog at the age of eight weeks.  He has always been very dominant and bossy.  My Leonberger is very soft and placid.  The newfie is very food orientated.  In the last few months he has become very aggressive with food.  I always feed them separately.  Even when I bring my shopping into the house the newfie goes for the older dog.  As soon as I take the dog bowls out of the cupboard the newfie will look to see where my other dog is.  I put the younger dog the other side of a child gate and feed the older dog in the kitchen.  Yesterday my husband took the bowls and accidently forgot to shut the childgate. Both dogs followed him to where the food is kept.  All of a sudden the newfie went for my older dog.  This time he drew blood on his face.  Fortunately just missing his eye.  The wound was not deep so has not needed stitches.  We love both of them but are at our wits end as to know what to do.  The worst scenario will be having to let the newfie go to a new home.  We don't want to do this without giving him a chance. We have owned a newfie before and he and my leonberger used to eat their food on a cloth together.

The only thing I can think you can do is do what you have been doing feed them seperatly ,If you cant find a soloution  Id get a behavourist in before deciding to let him go . she or he might have a better suggestion .

Hi
Well i've had newfies for 20 years and can honestly say i have never had an aggressive one, but i have sold pups, all males, who have become dominent agressive with new owners. i have been able to retrain these dogs over 4 - 6 weeks but it is not easy.
It is always due to owners not becoming the alpha, pack leader, the dog then adopts this role.

If these were my dogs i would make the newfie wait for everything, toys food whatever until the leo has had his first - it the newfie is agressive at all for any reason, throw him outside roughy, be vocal with a growly type voice, and leave him there until he behaves (newfies hate being outside on thier own)

He must learn that he has to behave to get what he wants and that the leo has to get things first.

Hope this helps and let me know how you are getting on.

Sharon