[feldon34]

I am able to use a variety of mp3s from various sources in Marine Aquarium 3 Beta 6 with no problems.

It took me a few to figure out the setup. I went into Settings, removed Pachabel from the list, then added a bunch of mp3s from different sources encoded by different people (including myself). I went back into the Aquarium and it was still playing Pachabel. I pressed F8 which I guess stops the music and then F9 which after 2-5 seconds, a random song from the playlist starts up. I alternated between F8 and F9 and was able to play all of the songs I added to the list successfully.

EDIT: I should add that by closing and restarting the Aquarium, I've eliminated that 2-5 second delay between pressing F9 and getting the next song to play. It starts almost immediately.

I wonder which version of the mp3 codec you have installed on your PC.