Jan, what a sweet thing to do for your Mom! I love aquariums and use to have one but like your Mom, I could never keep the little guys alive for very long.
It made me feel so bad that I disasembled the aquarium as I couldn't take seeing them floating at the top all the time.
Here's wishing your Mom the best with the new fish and many hours of enjoyment watching them swim around!
Take care,
Linda