Commander Shepard is a busy spectre. Running around the galaxy, shooting reaper scum, and trying to save the day. So I don't begrudge her buying some fish to at least make her quarters look a little nicer.
But at the same time, Shepard spends so much time flitting about, that... well, let's just say that Earth isn't the only place where Organic Life is dying out.
In Mass Effect 2, Shepard could eventually enlist Kelly Chambers to feed Shep's fish (she even returns them when you run into her on the Citadel!), but Kelly's no longer part of the Normandy's crew, and so Shepard's aquarium lies fallow.
Is there some way to automatically feed the fish? Is there no hope for these piscine soldiers? Is there no way to prevent them from dying every time Shep goes on a mission without feeding them? Forget Palavan or Earth, think of the Fish!