How to Make a 125-Gallon Fish Tank

There's no doubt that a fish tank is an eye-catching centerpiece for any room. Fish are mesmerizing and relaxing to look at. But the drawback is that store-bought fish tanks are expensive! Making your own fish tank is a far more cost-effective way to provide a home for your fish. A 125-gallon fish tank made by a well-known brand such as Perfecto Aquarium can cost several hundred dollars from a retail store.

Zebrasoma Yellow Tang in saltwater reef aquarium tank
How to Make a 125-Gallon Fish Tank
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You can build a 125-gallon aquarium for large fish with a few simple materials. When fully operational and full of water, this tank will be very heavy and hard to move. Before getting started on building your tank, set up a stand for it and set the whole thing up in a permanent place in your home.

125 fish tank dimensions

The My Aquarium website says that one benefit to setting up a large aquarium like a 125 fish tank, as it is sometimes called for short, is that it is easier to clean than a smaller tank. They don't need cleaning as often, and toxins don't build up in the water as quickly as in smaller tanks. And, of course, a larger tank means you can keep larger fish.

A 125 is a centerpiece tank that is the kind you see in doctors' offices and office buildings. It's a large piece that, when filled with a large fish like an Arowana, is impossible to ignore. The 125 fish tank dimensions are about 72 1/2 inches x 18 1/2 inches x 23 3/8 inches, according to Kerns Analysis on its fish tank size guide.

125 fish tank stand

The width of 72 inches is equal to 6 feet. Kerns Analysis says the empty weight of this 125-gallon aquarium will be 206 pounds and it will be 1,440 pounds when filled with water. Your 125 fish tank stand will need to be able to support this considerable amount of weight.

Glass or acrylic?

The Fish Lab website says the question of whether glass or acrylic is better for a fish tank comes up often. Both materials are see-through, which is, of course, key for an aquarium. But the similarities pretty much end there. For beginners, Fish Lab recommends glass, because acrylic is easier to scratch than glass.

If you scratch your 125-gallon aquarium and put a scratch right down the center that mars your view, you probably won't be very happy! A second reason that many experts recommend glass is that it is less expensive for a piece of glass than acrylic. Acrylic is lighter and also more impact-resistant than glass. All of these are pros and cons that you may need to weigh to determine whether to use glass or acrylic for your aquarium.

Check around in your area for suppliers of both glass and acrylic and compare. Let them know that you want the acrylic for a large fish tank, and ask some questions about how to care for the acrylic. Their answers will give you the information to make the decision on what material to use that is best for you.

125-gallon aquarium construction

Constructing a 125-gallon aquarium is not that difficult. After all, it's all rectangles! But it is imperative that you have the right supplies and you put the items together properly. First, have your panes of glass or pieces of acrylic cut to the proper dimensions and make sure they fit the stand on which you'll place the aquarium.

Follow along on the Beautiful Dragons website as the site owner builds an aquarium.

Step 1: Prepare the glass

Lay the panes of glass on a flat work table. Using sandpaper, lightly sand all sides of the glass to file down any sharp edges. Apply acetone to a paper towel and wipe the glass down from about 2 inches to the edge.

Step 2: Cut the tape

Using your scissors, cut about eight strips of duct tape. These strips should be about 6 inches long. Stick one end of each strip to your work table until you are ready to use the tape.

Step 3: Label the glass pieces

Label your glass pieces with your washable marker to remind yourself what pieces will go where. The three bigger pieces will be the bottom, front, and back panels. The two smaller pieces will be the ends.

Step 4: Assemble the pieces

Lay the bottom panel in front of you horizontally. Take the back panel and a side panel and line them up in their appropriate positions along the edges of the bottom pane. Use two strips of tape to secure the back and side pane together.

Stretch the strip of tape from one pane to the other. Repeat this step with the other two panes. You should have a glass rectangle box without a top. The strips of tape should be holding each corner firmly together.

Step 5: Seal into place

Inspect the shape and alignment of the rectangle. Squirt a bead of silicone into one of the corners at the bottom of your tank. Continue applying silicone along the crack, sealing the bottom edges together. Use your finger to push the silicone deep into the crack as you smooth the surface of the sealant.

Repeat this process for all corners of the tank.

Step 6: Clean up

Let the silicone dry for a couple of hours. Use your razor blade to remove drips or messy silicone spots.

Step 7: Check for leaks

After 48 hours of drying time, fill the tank half-full to check for leaks. If it is completely sealed, carefully wash the tank to remove impurities.

Step 8: Fill and assemble

Fill the tank with water. Place your decorations, pump, and other items that will go inside your tank. Then add your fish!