Hi guys,
Spotted this one a bit late, sorry.
Im happy to help if I can but need to figure out a way to do so that will make sense and encompass some information thats going to be of use.
If you can find that EXIF data for the image that would be of great use. Hosting sites like facebook etc strip that as its unecessary weight. There are quite a few EXIF Viewers in the public doamin to make it easier to access.
EXIF is your friend. As an example, if you take three or four shots at different settings and three are blurry and one great, the EXIF will let you pinpoint what changed to make it work.
As mentioned above - a Tripod helps massively. Im always handheld for stuff like this but then my camera has a few toys to allow that luxury. Id recommend a tripod strongly.
Anyone reading this who wants to move to manual control of the camera to really bring the camera to life needs to understand the exposure triangle. To save me waffling on for hours, this site nails it down very well.
http://www.cambridgeincolour.com/tutorials/camera-exposure.htmPay attention to ISO.
Thats the cameras sensitivity to light, and whilst your aquarium may look bright, compared to daylight it really isnt... its very dark. Your going to have to shoot with high ISO in most aquariums and sadly, thats where most cameras fall down. High ISO = High noise.
I need to get to bed as ive to pick my little girl up from Lancaster in the morning, but I hope this topic grows and I will try to add some value to it tomorrow night. Framing properly can make even a dull image interesting, I will try to explain a few golden rules for composition that may help.