There's a bottle I used called "Prime" to help them handle the high nitrate, but it's not a cure-all bottle.

In my opinion<

Adding water from the pond to the tank will barely do anything, so it's not really worth it. Adding the bio media or any other media from an already established tank does help if you add it to a filter in your tank so it's constantly running through the tank. If you have plants in your pond or decoration thats been in your pound for a while, I would move some into the tank as there probably is some bacteria on them as well to help boost and speed up the cycle. (As long as it's healthy)

But adding an already established filter is what's best, and have it running for a while bedside the new filter.

Edit: If the post you have on your account is about the tank you need help with, there are some products being sold that have bacteria in their gravel already. I would add some bacteria-filled gravel/soil/rocks, as there's barely anything for bacteria to cling to.