Yes, it is really tricky shooting through glass. I too have noticed distortion if I deviate at an angle. Often, I think aquarium photography is a game of chance. By that I mean having your subject matter come into a desirable view, then having your light and aperture/fstop just right at that exact moment, and finally, having it all in focus. All these things and more come together in a photo that is above average.
Often, I'll bracket my shots so I can increase my chances of having a decent exposure. And of course, keeping the camera steady on a tripod, sometimes using an infrared remote control. I'm finding most of my pictures are bad because my camera is old, the lens is weak, and I'm usually unable to tell if I really have things in sharp focus. So I'll lean on photoshop to get things looking more how I see the subject matter with my eyes. My camera and I don't always agree.
I'll use these PS filters & routines often: Unsharp mask (when scaling down an image), Reduce noise (if my ISO speed is too high) and Shadows/Highlights (if my shot is under exposed). Sometimes I will jack up the saturation just a tad because I notice the "Save for web" jpeg compressor will desaturate my photos for some reason. Personally, I have no aversion to post-production touch ups with photos. I did all kinds of experiments in real dark rooms in the past so it's quite natural for me to carry on with digital tricks. Healing brushes, etc.
The ring light idea in the article is kind of interesting. Might be really useful for macro shots. Anyway, looking forward to more shots from you. I'm off to the Gallery to see your new stuff. Good luck capturing that perfect harlequin shot!