Hi Dan
nice tank and fish

re your water changes see below
Had the same problem as you, had two large tanks against a wall and very soon realised the one for our 2 oscars wasn't really big enough, so bought a new 150 gallon,
AND it needed to go where the current one was, so like you had to place the new one close and transfer water etc to new one, half way moved the fish, then emptied old tank,
moved old out, and then from new tank moved everything back to old tank, and then moved the new one into place, and finally all back from old tank to new one, moving the 2 oscars 3 times was fun and games and plenty of splashing all over new wall paper lol, ,the water wasnt to big a problem as i used a pond pump to move water from one tank to another, and less stress than pouring water on top of them, i now use the pump when doing water changes, straight from plastic dustbin to tank, i use another bin with a gravel cleaner to extract dirty water to,
i think the easier you make water changes the more likely you are to do them, otherwise if it becomes a chore you may leave it longer than you really should