Just downloaded it and looks great so far...
As a newb to reef tanks, something that I would find useful would be the ability to keep track of what's actually IN the tank in terms of livestock. Obviously, with the variety of stuff out there, there's no way to do this via drop down - but perhaps a specific section (Aside from notes) where this could be added?
i.e. have a header called "cleanup crew" - where I could manually list what I have, and perhaps have a +/- slider to indicate how many? That way as I notice "oh crap, 3 snails died" I can adjust and keep track, and know when its time to buy more?
Perhaps even add a social networking piece to it where one could share out their tanks stats, livestock list etc.
I am by no means a programmer so I'm guessing what I'm rambling about is excessively difficult/stupid, but figured I'd throw it out there