I love the tank, but I really hate that 1960's Tupperware gravel. Since you have a lot of greens and dark logs, why don't you go with a more natural stone, like riverbed tan or brown rocks?
That gravel seems kid-ish, or circus-like... Reminds me of cotton candy, or a gum-ball machine. Also, try and find a forest background, or tropical background, the water-scape background looks out of place.
Just my opinion! Great work, also try adding some floating leaf plants.