For those of you that are like me, you may not be able to justify an SLR just for your fish tank photos and you don't want to carry around an SLR everywhere you go. That is why you own a point and shoot camera that you can toss in your pocket.
There is a project on the web to enhance the firmware of a lot of Canon point and shoot cameras. Simply put, it has a temporary software upgrade that gives you more control of the hardware. I find this particular useful during tank shots, where the automatic functions just don't judge lighting well enough.
is a good place to start reading about the features to see if it's for you.
It's completely removable and doesn't void the warranty on your camera as the firmware is just put onto your SD card and loaded as needed. It can be set to autoboot or you can manually boot it. Removing it is as simple as not booting it or deleting the files from your memory card.
I just read what I wrote and I sound like I'm advertising for these people, but I'm just super excited to be able to have some real control over my camera. Besides, it's a free download.