Hey Snowman, I use a Canon 20D. Obviously, this helps a lot. However, I have several steps when taking a FTS.
EDIT: I forgot... Step 0. make sure the glass is clean, and the lights have been on a while, so the corals are "awake."
1. Square up with the center of the tank, left to right.
2. Raise the camera on the tripod until the top of the overflow teeth reach the bottom of the trim. Make sure the camera is shooting level. This way, the lens of the camera and the tank glass should be exactly perpendicular.
3. Lower ISO as low as it goes (ISO 100, in my case).
4. Raise aperture to about f/8.
5. Use the timer, even with a tripod. Or a remote. You don't want your hand touching the camera while it's shooting.
6. Underexpose the photo by 2/3 EV.
7. Go to Photoshop.
Photoshop (All actions are intended to reproduce what's actually seen, not fake it):
1. Crop photo down to all edges of tank. Bottom corners will be narrower than top, because of perspective.
2. Go to Edit/Transform/Perspective and make the bottom square by stretching it to the edge of the image.
3. Use the Heal Tool to get rid of blemishes, specks, or even snails in the wrong spot.
4. Auto Levels. Auto Color. Image/Adjustments/Match Color - Neutralize. Work with this combo, sometimes it pulls out too many blues.
5. Bump saturation about +6 to +8, to make up for some loss in the camera.
6. Potentially increase contrast.
7. Resize image to 800 pixel width
8. Smart Sharpen (typically 400-500%, radius 0.2, Remove: Lens blur)
9. Add border, save as jpg, as high quality as I can while keeping it under 200K filesize.
That was the quick-n-dirty no explaining version. You asked.