I have found the area to get the fish form, finally.
Now the issue is that I can't figure out how the symbols go! I found a something from gamefaq.com that lists all the songs, and the symbols for each, but some of the symbols that are listed for the fish song don't match the ones found in the room!
http://mods.whahay.net/Jester/aquaria/aquariamap1.jpgThe ones they list are: green seed, pink tear drop, orange sun, fushia circle.
The ones in game are: green up-side down heart, fushia circle, orange sun, yellow heart.
Two conflicting sources suck.
Could someone give a nudge in the right direction?