I used to own a tropical saltwater aquarium back in the late 90's to early 2000's, and I've raised over 30 different species of tropical saltwater fish in the tank, including coral and live sea anemones.
I came to realize that some fish are extremely smart, and they recognize their owners like pet dogs and cats, especially the lemon peel fish and picasso triggerfish. They also are very sensitive and they have feelings like humans do like being sad and happy. I also found out that certain fish are extremely freaked out by certain colours such as the blue damselfish would completely freak out if it sees anything that is hot pink in colour. Freak out meaning if would hide behind coral if it sees that colour.
There was one time we bought a bunch new smallish sized fish - I can't remember the name - in the aquarium, and the next morning they were all gone since they were all eaten up by one little fish called an orchid dottyback which sported a huge stomach.
If anyone is planning to own an aquarium, I recommend going for a saltwater aquarium because the colours of the fish and sea anemones under artificial lighting is absolutely amazing. I haven't been inside a saltwater fish aquarium store for more than a decade, so I don't know about the prices, but the hobby is very rewarding and relaxing. You will have much more compassion and appreciation to all fish in general.