In my opinion, aquaristic is a very useful term that is highly underutilized in the English language. That's why I am using it a lot on this site! Wikepedia defines an aquarium as a:

vivarium [...] in which water-dwelling plants and animals are kept in captivity [...]. Animals in aquariums usually include fish, sometimes invertebrates, as well as amphibians, marine mammals, or reptiles.

It goes on to describe 'aquarium keeping' as a popular hobby around the world, and calls people engaging in the hobby 'aquarists'. The term 'aquarist' is well established, but have you ever heard somebody talk about 'aquarium keeping'? I haven't. People tend to talk about their aquariums, and the whole article dealing with our hobby is found under that term on Wikipedia. However, I'd argue that for most people the fascination is not with the aquarium itself, but with what's in it, and it's not just about 'fish keeping' either. Certainly marine enthusiasts have always housed a wide range of invertebrates, and ever since Takashi Amano introduced Caridina japonica into the planted tank, the list of freshwater invertebrates available has been growing steadily. And did I just mention planted tanks? For many people with this variety of the addiction, the main focus of a tank is not necessarily fish, but plants. So what shall we call 'the hobby'? Well, if a chemist deals with chemistry, a physicist with physics and a mathematician with mathematics, it stands to argue that an aquarist would deal with aquaristic.