Whatever you do never plant a gum! They have no place in suburban areas! The sooner the council realises that these trees kill people the better! We have had two gum trees fall on the back of our house now, one in 2012 and one in 2014. We are so lucky that myself, my husband, three children, three dogs, five Guinea pigs, two parrots and one bearded dragon were not injured. It's just a miracle not once but twice! I still don't know how we escaped unharmed. The gums do not have a stable root system and they grow very shallow, they get to the point where they just fall over. And the scary thing is they fall silently. They are not called 'Widow Makers' in the bush for no reason. I like the Tuckeroo tree, not sure of scientific name. They grow with a straight trunk and keep their foliage in a straight and symmetrical line along the bottom and grow hiding their branches. Essentially they look like a large mushroom. They are green all year too. I think they get to about 6 metre or ten if they have to reach for the sun.

Luke, don't mess around with gum trees. As beautiful as they are, they are prone to falling suddenly and unexpectedly and that is one huge tree that could take out a couple of homes in the process. I've also found that if part of a tree dies, it can affect the balance of the rest of the tree so it becomes unstable even though it may look healthy. If an arborist says it needs to come down then I wouldn't waste time, you could void your insurance by not heeding advice. Do you need Council approval? Sometimes that can take a while to get.

That looks like an odd shaped, narrow angled back corner of the yard. Previously the big peppercorn tree filled it out, softened it and it looks like a cubby house enjoyed the cosy, secret corner behind the natural screen. One idea would be: firstly, get a stump grinder in to remove the stump which will otherwise limit any planting; secondly, plant a curved hedge of a suitable shrub (Murraya, bottlebrush, lilypilli...). Leave an opening at one or both ends of the hedge screen for access to the "secret corner". This might improve the shape of the yard and provide a useful utility area for compost bins, a small garden shed or other unsightly items.

@ alchemy, I can see you've put allot of effort into your beautiful yard and pool and whist I agree that you will probably regret a deciduous tree, irrespective of it losing most of its leaves in a short period, it would be allot of work clearing that debris from your pool but I agree that you need to complete your yard with greenery. I think the ficafolia suggested by bigreader could look stunning but I have one in my yard (no pool) and the gumnuts this little tree of mine drops must be seen to be believed albeit they dont blow. A palm of course is one of the best trees due to its lack of debris and the tropical look it provides is always a winner, however, getting one fairly established would be the way as they don't grow super fast but the expense of such a tree could be quite prohibitive. I would seriously listen to advice offered by people with an outdoor pool as experience is the best teacher, so you must decide just how much work you want to give yourself over and above the normal workload simply having an outdoor pool and I'd strongly consider the suggestion Mel N offered of putting up a sun shade or sail initially and see how that works for you. Best of luck. Cheers, Barbara