It came across as all good. Hope to meet up with you soon! Best way to learn is keep shooting.
Some things to keep in mind:
Keep the camera as still as possible. Using a tripod is good. If you do not have a remote shutter release cord, try and set the camera on a timer to avoid any camera shake too.
Keep the camera lens at a 90 degree angle to the tank to avoid distortion from the glass.
Think about your depth of field. Is everything in focus that you want to be in focus. An [smaller] aperture [number] like f/2.8 gives you a more narrow depth of field. The larger the number (f/10), the more light (longer shutter speed) you will need.
The longer the shutter speed, the more noise and graininess you can introduce into your picture. Too narrow a depth of field might meen you loose detail. It is a balancing act.
Use your exposure meter when viewed in the camera to make sure your depth of field and shutter speed give you a properly exposed photo.
Practice, Practice, Practice - Shooting in manual mode is going to be your best friend one day.