It's a great start, and once my tank clears a little more, I will try and ost some good examples (as opposed to the numerous bad ones I am so faithfully committed to taking) and the settings.
As a start, I reccomended the use of a few different types of filters for the SLR variety. A UV Haze filter cann help a litte (can make the flourescents a little muddy), or a step up to a polarization filter that can really get you a crisp image and cut out refraction (the thing that causes the light areas to wash and the colors to be muddled).
At minimum, a UV haze filter is a great cheap investment as it will protect your lens. After 30 years of clicking pics, I have saved some pretty expensive lens by scratching the filter instead.
For all, turn off that flash!!! the flash will not help you much unless youe tank is clean as air and your right against the glass....which is number 2. Go ahead and get right on the glass (after you clean it). Often the glass is of little factor as long as your really close.