I like your exhibits.
You might like to experiment with the foliage mixes. The animal will tell you if it does not like something - frowny face.
You can still achieve 100% using mixes.
For example when I do the Bengal tigers I might put one mangrove tree, one foxtail and a couple of ferns all in one tile. Another thing is some rocks, like the small rock, are water placeable so that is sometimes a good place to put them.
If you want ideas on what you can achieve in looks, have a look through the screenshot threads.