Here are some design ideas for turning an ugly corner into a mini landscape realistic waterfall aquarium using cement:

Create a Waterfall: To create a waterfall, you can use a combination of cement and rocks. First, create a frame of rebar and mesh wire in the shape of a waterfall. Then, layer cement over the frame and embed rocks of various sizes into the cement to create a natural look. Once the cement has dried, use a water pump to create a cascading waterfall effect.

Add a Pond: To create a pond, dig a hole in the ground and line it with a rubber liner. Use cement to create the edges of the pond and make it look natural. Once the cement has dried, fill the pond with water and add plants and fish.

Create a Landscape: Use cement to create a natural-looking landscape around the pond and waterfall. Use rocks, sand, and pebbles to create a natural-looking environment. You can also add plants, trees, and other natural elements to create a realistic landscape.

Add Lighting: Use waterproof lighting to highlight the waterfall and pond. This will add a beautiful and dramatic effect to your mini landscape. You can also use lighting to highlight specific features such as plants or rocks.

Choose the Right Fish: When choosing fish for your pond, make sure to choose the right species that can survive in the conditions of your mini landscape. Some good options include koi, goldfish, and guppies.

Incorporate Sound: The sound of running water can be very soothing and relaxing. Use a water pump to create a gentle waterfall sound that will add to the ambiance of your mini landscape.

Overall, with a little creativity and some cement, you can turn an ugly corner into a beautiful mini landscape with a realistic waterfall aquarium.