DIY Square Tank

Determine the dimensions for your tank. When building a square tank, the length will be equal to the width of the tank. Utilize an online aquarium water volume calculator to see how many gallons of water your proposed dimensions will hold. For the sake of cost-effectiveness, it is not recommended you build a tank less than 50 gallons in capacity.

Determine the appropriate width for the glass in your aquarium by consulting an online aquarium glass thickness chart, using your determined dimensions for reference. Keep in mind that most glass thickness charts are designed for rectangular tanks. For a square tank, use glass no less than 8 millimeters thick.

Purchase tempered sheet glass to use for the sides and bottom of your aquarium and have an in-store professional cut the glass to the sizes you require. You will need four sheets of glass equal to the length and height for the sides of your tank and one sheet cut using the length and width measurements for the bottom of the tank. You will also need four 3-inch sheets of glass cut to the length of the tank to be used as cross braces.

Sand the cut edges of the glass using fine-grain sand paper. You may also choose to slightly round the edges with sandpaper to prevent cuts when handling the glass and the finished aquarium.

Lay the sheet of glass serving as the tank bottom on a flat surface in front of you. Cut eight 6-inch strips of duct tape and stick one half of each strip to the under side of the glass so the remaining sticky side sticks out. Position two strips on each of the four sides of the glass, evenly spaced.

Apply a generous bead of silicone aquarium sealant to the bottom inside edge of one of the four glass side panels. Hold the panel at a slight angle away from the bottom panel, aligning the bottom edges. Gently lift the panel into a vertical position as you press the edges together, creating a seal with the silicone sealant.

Fold up the two strips of duct tape on the corresponding side of the glass tank bottom and stick them to the side panel you just attached. The duct tape will keep the glass panel in place while you attach the other side panels.

Attach the remaining three side panels following the same procedure as the first, securing each in place with the two strips of duct tape when finished. Once all four side panels are in place, apply a generous bead of silicone sealant along each interior seam. Dip your finger into a small bowl of rubbing alcohol then swipe it across each seam, spreading the sealant as you go and concentrating especially on the corners.

Apply a bead of silicone sealant to the two short edges and one long edge of one of the 3-inch sheets of glass. Align the long edge with the top edge of one of the side panels and press it down gently, also aligning the short edges with the top edges of the perpendicular side panels. Repeat this process with a second 3-inch sheet of glass, affixing it to the side panel opposite the first. These two sheets of glass will serve as cross braces.

Apply a bead of silicone sealant along the short edges of the remaining 3-inch sheet of glass and lay it across the width of the tank, perpendicular to the first two cross braces and centered on the top of the tank. Gently press down on the glass to form a seal with the silicone sealant.

Allow the sealant to cure for 48 hours then fill the tank with water and let it sit for 24 hours to check for water tightness. If the tank does not leak after 24 hours it is safe to use. Empty the tank, rinse it well, then refill it and set it up in your desired location.