I've thought about the answer to this question a lot. Defining an aquarist is easy. There is a standard definition. However, the word doesn't mean the same thing to everyone. In fact, ask a group of aquarists what it means to them to be called an aquarist and you'll probably get different answers.
As I sifted through the myriad reasons why I keep fish, I began to see a pattern. Since my youth, I have been mesmerized by freshwater and marine ecosystems. I grew up spending summers on a local lake where my family owned a houseboat. I went to college intent on becoming a marine biologist, though that never panned out. Nevertheless, I've always been naturally curious about how things work, which includes biological systems, and I've always been especially intrigued by fish and marine mammals.
Some might argue that aquarists are fish lovers. I would support that definition. Then again, there are some who keep fish more for the fun of watching the aggression or predation. In other words, some enjoy watching their fish hunt and consume live food. Those fish keepers might be aquarists in the strictest sense, but they're not aquarists to me. Just like I wouldn't call someone a dog lover who raises dogs to fight other dogs or raises dogs to hunt rabbits, raccoons, etc.
I sincerely care about my fish and I don't like it when one dies, regardless of the reason. I enjoy the behavior of cichlids - the parental care, the defense of a territory, the individual personalities, etc. I could go on and on.
Is an aquarist an expert in fish keeping? Sometimes.
Is an aquarist someone who values the life of other species? Maybe.
Some aquarists do it as a vocation. Some do it as a hobby. Some do it for the challenge.
If you're reading this, I suspect you have more than a passing interest in fish. If you keep fish, why? What does being an aquarist mean to you?
The Cichlid Room Companion
Tropical Fish Hobbyist
American Cichlid Assoc.
African Cichlid Hub