After a month of work, I can finally present to you the completed aquarium. It proudly houses four kinds of plants and three species of fish. For the water on top (I had to cheat there a bit) I partly drew on the Shader Forge courses, and I used a few tips from 'Fundamentals of Compositing'.
Blog post: https://honestmisskate.blogspot.com/2017/10/freshwater-aquarium-final.html