The oldest I can find on my hard drive are....
v99L (Aquarium99L.exe 13/09/2001)(1.132 KB)
v1.1 (AquariumV11.exe 21/02/2002)(1.028 KB).
v1.1wide (AquariumV11-wide-0328.exe 27/06/2002)(1,051 KB)
But I can't get the 1.1wide to work correctly on a modern LCD, -
the way it did on a Sony Trinitron CRT, ie wide-screen. - It's now all squished tall and thin, and full screen height!