Hi Mery,
Welcome to CC!! There are a few links already about this very subject.Try doing a search and you should come up with lots of info...if not someone will be around shortly to give more info!!!
No the iP1600 isn't yet compatible with the edible ink cartridges that are available. This may change in the future. KopyKake is working on new style cartridges. Not sure of the release date yet or exactly which printers they'll be compatible with but it will be the newer Canon models.
For the Canon iP3000, you need the 6000 set (4 cartridges). They look like this...
http://store.kopykake.com/cgi-bin/oldstore/6000-SET.html
You can also find a great deal of info here...
http://www.sugarcraft.com/D-pictures.htm
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