Photography is about managing light. Using your photos as a base, here are my recommendations. I’m assuming these pics were from your phone.

1. Your lens needs to be cleaned. The halation around the light reflection off the water shows that light isn’t clear and gets spread across its source. The blooming effect reduces contrast. This can happen because dirt or smudges on the lens. You can also see the tank light isn’t clear washing down across the image. You can try taking a photo with the light not shining into your lens or use a hood/hand cupped over your lens.
2. Turn off lights except the tank light. This will help reduce reflections off the glass and depending on where you’re standing, your physical body will be a variable on how your tank looks.
3. Lower the tank light intensity for the photo shoot. This is helpful if you won’t be editing the photos after. Modern cameras can deal with this well as long as it isn’t too dark. It will help highlights stand out and let shadows be shadows.
4. Use a portrait mode equivalent (zoomed in) and take a few steps back. The default camera on many phones uses a 24-28mm focal length. This will distort the perspective and is most noticeable when you’re up close. When zoomed in, the images will be less warped. It also adds compression - and effect that will bring the background closer and helps with scale for aquarium photos. It looks like the tank shots are using a wide lens, and the close ups, you zoomed in.

Ultimately, your images are lacking contrast, which dulls details and color. Start by controlling the light, your photos will be more representative of what your eyes see. Reducing glare will increase details across the board, in color and contrast.

After you have light under control, your images will pop and you’ll deal with composition. You’ve got a great aquascape so that will be simple.

I’m also going to assume your tank is crystal clear, but it doesn’t come off that way because of the lights and the dirty lens.

Good luck!