First off, cool tank! I think it's really going to look excellent as it fills in. With regards to your photos, I can give you a few tips. The first thing I'll say is that you either pushed saturation in your most recent photos, or you are doing it in camera. Either way, I'd avoid that, as it makes the tank look unnatural. You lost tons of detail in your greens and the reds look off.
For taking photos of a tank, here is a list of tips off the top of my head:
- Use a tripod and a remote shutter release or a timer, it makes a big difference
- Use the lowest ISO you can get away with (this is why the tripod is needed)
- Use the highest aperture (f-stop) you can get away with (also why the tripod is needed)
- Turn off your pump about a minute before you shoot, and let the water stop moving the plants
- Shoot in RAW, or set things such as vivid to neutral or 0
- The closer you are to straight on square with the front of your tank (left to right and top to bottom), the sharper
- Play around with zoom and the distance your camera is from the tank.
A low aperture number will give you less objects in focus. If you can shoot at at least f-8 and ISO 100-400 on a tripod, that will go a long way. The only thing that may get motion blur is your fish, as long as your turn off your pump.
Shooting straight on makes a very big difference. As you get off center, the water distorts things and causes chromatic aberration and less focus. Shoot square to the glass, and things will be much sharper. I know this limits your options with shooting angles, but the more off square you are the less sharp your pic will be.
With regards to distance, I tend to shoot about 4' from my tank and zoom in a little. But try shooting closer with a wider angle, or a little further way and zoomed in more. You'll get a different feel from each one.
Rather than just snapping a pic, play around for a half hour and test out different settings. Compare them and see what you like.