The game is a music-making tool where players manipulate neon fish in order to produce various sounds or music. There were ten different musical programs in the retail version of Electroplankton. These programs will be split up into separate releases on DSiWare for 200 DSi Points ($2) each.
Here is the release schedule for the Electroplankton titles in Japan:
July 8: Tracy, Hanenbon, Nanocarp, BeatNES
July 22: Rec Rec, Lumiloop
August: Sun Animalcule, Luminarian, Marine Snow, Volvoice
There are currently no plans for release of these titles outside of Japan right now.
I understand it was supposed to a musical experiment and not a game, which is why $35 was a rip-off price.