hello,
i went through the same thing with skits my water dragon, i got her in november.she was about the same size as yours, since then she has doubled in size, she has had 3 good sheds and her color is sooooo pretty now once I got the temps and humidity right. your aquarium looks good for now but as soon as possible you will need something a lot bigger and then you get to start all over again trying to get the humidity and temps right lol
my skits wouldnt get into her water on her own at first (i have a tub similar to yours) they just dont like the water that deep. i bought an underwater filter/pump ($10) and and some rocks and made a small fountain in the middle of the tub with a fake branch going into the water now she gets on top of the rocks under the fountain and it looks like she is washing her hair!!! (scales!) lol I have to change the water every other day and scoop poop every day but she loves the fountain so its worth it.
another trick with the crickets is to get some of the bamboo tongs and hand feed or pull the back legs off of them before you put them in with your dragon, they cant hop so they are easier to catch
hang in there it gets easier and the people here are very helpful so listen and learn
good luck
chris

oh I have to see a pic of this waterfall!! do you have any pics? I seem to have the temperatures ok except maybe the water because he doesn't go in that often. I do catch him in there but lemme tell you if a dragon could give a dirty look - then he gives me one whenever I catch him in there!