Dog on dog aggression?

Hello, I'm wondering if anyone could help me, I have 2 dogs. A six year old taffy who is soft as muck and no bother.

I also have a two year old make german shep and he is aggressive towards other dogs. In the house and with my other dog and pets he is brilliant, and even when out on walks he is well behaved UNTILL their is another dog. It is when we see another dog his ears stick up, he watches them, he then starts to lunge bark and go sort of 'crazy' as I would describe it. He is a brilliant dog UNTILL it comes to this matter. I have tried almost everything possible I could think, read or watch on dog aggression ect.

So I was wondering if any of you wonderful people on here would be able to give me a bit of advice and share your story's about any dogs you have had with dog on dog 'aggression' would be brilliant to hopefully get new ideas.

Thanks.

Well for a start it can be corrected, for me and with dog at 6months old i noticed he was a bit sharp with other dogs so being a rescue lurcher i was looking for faults of which this was his only one, so what did i do well ive no time for nasty or aggressive dogs so out i went to car boots for some crowd and hopefully some other dogs, lots of people helped and with dogs also in sight that also helped, dont let your dog get too close yet but in time see if he settles with a certain breed then with him under control see if he will play nice, now im old school so no dog is going to rule me so my dog soon got i idea of what i accept and what i dont, end result has been 12 yrs of no hassle, best of luck in your efforts..

Have you had this GSD from a pup? Look into reputable dog training classes where your dog can meet others and develop his social skills and manners in a controlled environment.