Use current water/ornaments and live plants for quick set up of new tank

I have upgraded from a 15G tank to a 20G long tank (petco had their $1 per gallon tank sale!) and I was wondering if just taking some of the old water from my axie's 15g tank, plus the ornaments/hides (unwashed) and use those to keep the good stuff in his water. Would it be like a partial water change? I do not use a filter for him (but thinking of getting him an external filter with a spray bar like my turtle has). I also have some new live plants and the water is fine now (just the ammonia is at .5, so a slight spike). Would he be okay for a quick transfer? He is a golden and about 7inches. I read some where else that this would be ok, but want to make sure!

Not really sure how to "follow" this post, so I am writing on it to hopefully keep better track of this...

I also am very curious about this..

I heard that as long as you keep the levels pretty close to in check then it should be ok, but there will still be some of a cycling process. When I first got him at 4 inches, I was not expecting him lol Talked to the breeder and he said that they are the easiest things. Told him that I had an empty 10 or 15 gallon, could not remember at the time, and asked what I had to do to get it ready. He said just fill it up about 1/2, use conditioner of course, and put him in. He was little then and had no problems. He also said not to worry about testing as long as I clean up after him and change the water 20% every other day. And Pinky never seemed stressed, greeted me at the glass or top of the tank, ate and went potty very well! Now, after reading more about them, I have done testing, thinking that my ammonia level is at .5 due to a kind of 'gentler' cycle? But still doing the 20% daily or every other day. I know that there are some people that say that they have never cycled, some that always do a full few week cycle, so I am just curious.