No Limit To Aquarium Ideas
The number of different aquarium ideas is practically endless once you get into studying the topic and see what others have done. Once upon a time, aquarium ideas were seemingly limited to a goldfish or two in a bowl, with a bubbling deep sea diver placed on the bottom for decoration and water oxygenation. It's easy to come up with something better than that.
A trip to a local aquarium can often be a source of good ideas, especially if there are some smaller tanks that have been decorated. Even the larger 10,000 gallon or more sized tanks, when suitably decorated (architecturally designed may be a better word), may provide some home aquarium ideas, if you can figure out how to scale things down.
Assuming your decorating scheme is fish friendly to begin with, the inside of the tank can resemble a tropical rain forest with a wide variety of vegetation, a Japanese sand garden with a very few carefully positioned objects placed on the bottom of the tank, or something which simply resembles the natural habitat of the occupants. Don't stop there of course, the only limits are those of your imagination, and the well being of the fish.
Tank Variations - While the tank is most apt to be a standard rectangular-shaped version, unless you want to get into customizing, it can be rather shallow with a broad surface area, or tall and narrow. Two of the most unusual tank ideas, both patented, are the "fish highway" where fish can swim through sealed tubes and channels running along the walls and ceilings of a room, and the phone booth aquarium, utilizing a genuine phone booth, complete with phone, adapted to be made watertight, and home to a number of fish (you feed from the top, not by opening the door).
On a smaller scale though, it's all about tank size and shape (keep the need for cleaning in mind), substrate, decorations in the way of plants, wood, rocks, or porcelain mermaids, lighting, and background effects. Given a carefully constructed background, a shadow box approach is often much better than an aquatic photograph or image, and with the right lighting, the aquarium can not only be made to be quite striking in appearance, but be made to appear much larger than it actually is, as you can use shades of colors, lighting, and placement of objects to give a perception of depth. Some aquarium owners simply paint the back glass of the tank black or some other color to make the fish and plants or decorations stand out.
Substrates And Interior Decoration - While there's nothing wrong with simply using sand as a substrate, and for some "interior decorating" ideas sand may be a perfect fit, searching for the right gravel and/or rocks can be half the fun. As a rule of thumb you want rocks and gravel that are somewhat similar in shape and color, if not necessarily in size, rather than a jumble of sharp rocks and round rocks, in various colors. This, and other rules of thumb, you can feel free to break at any time. It's your aquarium and you'll be the one who will be looking at it most of the time. The fish may or may not care.
Once you have the substrate in place, be it sand, gravel, rocks, or a combination, it's time to add plants, structures, caves, branches, and your porcelain mermaid. If you have an aerator, and you certainly would for most aquariums, try placing it where the stream of bubbles has the most dramatic, yet seemingly natural, effect.
If all you want is a tank of water with a few attractive fish, then all the above may not be for you. Obviously, when decorating and customizing a large aquarium things can get complicated and expensive fast, but if it just happens to be a hobby it's certainly one that can last a lifetime. You might even end up with a phone booth in your living room.