Building or repairing an aquarium requires a specific set of supplies, and using the wrong materials can be dangerous for your fish. The core supplies for aquarium building are aquarium-safe silicone sealant, glass or acrylic sheet, glass cutting tools if you're working with glass, acrylic cement for acrylic builds, and bracing materials for tanks over 30 gallons. If you are repairing a leaking tank, the main item you need is 100% silicone sealant with no fungicide or mold-inhibiting additives, since those chemicals will kill fish.
Whether you are building a custom tank from scratch, resealing a used aquarium, or fabricating a custom sump, this guide covers the materials, tools, and techniques you actually need.
Glass vs. Acrylic: Choosing Your Material
The first decision for any aquarium build is the tank material. Glass and acrylic each have genuine advantages, and the right choice depends on your build size, budget, and use case.
Glass
Glass is the traditional choice and for good reason. It resists scratching far better than acrylic, does not yellow over time, and is less expensive in standard sizes. For tanks up to about 75 gallons, glass is almost always the cost-effective choice. Float glass is used in most production aquariums, but for builds over 75 gallons, low-iron glass (sometimes called ultra-clear or starphire glass) is worth the premium. Low-iron glass has a barely perceptible green tint that becomes noticeable on thick panels in standard glass, making water look green from the side.
Glass thickness for a home aquarium follows established guidelines. For a 40-gallon breeder (36 x 18 x 16 inches), 3/16-inch (4.8mm) glass is the minimum on the bottom and sides. For a standard 75-gallon (48 x 18 x 21 inches), 1/4-inch (6mm) glass is appropriate. Tanks over 100 gallons typically use 3/8-inch (9.5mm) glass. Online calculators from sites like Glass Cages and custom tank builders let you input your dimensions to confirm appropriate thickness for your specific build.
Acrylic
Acrylic is lighter than glass (roughly half the weight), optically clearer without any green tint, and it can be bent and shaped into curved or non-rectangular forms that glass cannot. A 1/2-inch acrylic panel is stronger than 1/4-inch glass at equivalent sizes. For very large tanks (200 gallons and up) where weight is a concern, acrylic becomes the practical choice.
The downsides are real though. Acrylic scratches easily, requires scratch-removing kits to maintain, and solvent bonding requires more skill than siliconing glass. Plexiglas G (cast acrylic) is preferred for aquariums over cell-cast or extruded sheets because it is more optically clear and bonds better with acrylic cement.
Silicone Sealant: The Most Important Supply
Whether you are building with glass or acrylic (for acrylic, silicone seals perimeter seams while the structural joints use cement), silicone sealant is the foundation of a watertight tank.
What to Use
You need 100% silicone. Not "kitchen and bath" silicone. Not "tub and tile" silicone. Those products contain mildewcides that are toxic to fish. The label should say nothing other than "100% silicone" or "aquarium-safe."
Aqueon and GE both sell aquarium-safe silicone sealant. The GE Silicone 1 (original formula) in white or clear is popular with DIY builders because it is widely available and genuinely fish-safe. ASI (Aquarium Systems Inc.) also makes a product specifically marketed for aquarium use that comes in black, which many builders prefer for its finished look.
Black silicone hides algae and debris buildup better than clear. On a display tank, most hobbyists prefer black. On a sump or utility build, clear is fine.
Application Tips
Clean all surfaces with 91% or higher isopropyl alcohol before applying silicone. Even new glass has manufacturing oils that prevent adhesion. Apply the silicone bead to one surface, press the panel in place, and let the silicone cure before handling. Most aquarium silicone takes 24 to 48 hours to skin over and 72 hours to cure fully. Do not fill the tank with water until full cure. Running a bead of silicone along interior corners and smoothing it with a wet finger or purpose-made tool creates the fish-safe rounded bead that commercial tanks use.
Glass Cutting Tools
If you are sourcing glass from a local glass shop and cutting it yourself, or modifying pre-cut panels, you will need proper cutting tools.
A carbide-tipped glass cutter like the Fletcher Terry 07-078 Pistol Grip Cutter is the standard tool for scoring glass. Score once along a straightedge with steady pressure, then run the score to a corner and snap the panel over a dowel or edge. Do not try to score twice along the same line. Aquarium glass should have its edges sanded with 120-grit wet/dry sandpaper to remove sharp edges before assembly.
Alternatively, local glass shops will cut to your dimensions for a few dollars per cut, which is often worth it for larger panels where a bad cut wastes an expensive piece of glass.
Bracing and Support Structures
Tanks over about 30 gallons need center bracing across the top to prevent the sides from bowing outward under water pressure. Commercial tanks use a plastic center brace strip that spans the long dimension. DIY builders often use glass strips cut from the same material as the tank walls, bonded with silicone, or acrylic strips bonded with acrylic cement.
For a 55-gallon tank (48 x 12 x 21 inches), two braces spaced evenly across the top opening is standard. For a 75-gallon (48 x 18 x 21 inches), a center brace 4 inches wide spanning the 18-inch width is typical.
The stand matters too. A glass tank distributes its full weight along the bottom rim. Your stand must be level and flat. A stand that is even slightly off level creates stress on the silicone joints. Use a 4-foot level and shim legs if needed before filling.
For guidance on other aquarium equipment that pairs with custom builds, the best aquarium equipment roundup covers filters, lighting, and hardware suitable for DIY setups.
Acrylic-Specific Supplies
If you are building with acrylic, you need different bonding materials.
Acrylic Cement (Solvent Bonding)
Weld-On 4 is the standard thin acrylic cement for aquariums. It is a water-thin solvent that wicks into the joint by capillary action. You apply it with a needle-tip applicator bottle while the panels are held square, then let it cure. Weld-On 4 cures in about 24 hours but reaches full strength in 48 to 72 hours. Weld-On 3 is even thinner and cures faster but gives you less working time.
Weld-On 16 is a thicker gel-type cement used to fill gaps in joints that are not perfectly flush. Use it as a secondary pass after the initial Weld-On 4 bond.
Acrylic Cutting Tools
Acrylic sheet is cut with a scoring tool (similar to glass) for thinner sheets up to 1/4 inch, or with a table saw or circular saw fitted with a fine-tooth blade for thicker material. The Olfa Acrylic Cutter PC-L works well for thin sheet, creating a clean score line that snaps cleanly. Protect the backing paper until final assembly to avoid scratching panels during handling.
Miscellaneous Supplies Worth Having
Masking tape: Tape off areas around silicone joints to get clean edges. Remove the tape while the silicone is still wet.
Razor blades: A razor blade scraper removes old silicone and glue residue without scratching glass. A new, clean blade cuts through cured silicone without tearing.
Plastic or wooden shims: Keeps panels held at exact right angles while silicone cures. Painter's tape alone is not enough for larger panels.
Clamps: Acrylic builds need uniform clamping pressure while cement cures. Spring clamps or bar clamps positioned every 6 to 8 inches work well.
Leak test supplies: Fill to the brim in a yard or garage, not inside your home, and leave for 24 hours before moving the tank to its permanent location.
For more product recommendations to complete your aquarium setup once the build is done, the top aquarium equipment guide covers lighting, filtration, and heating options across different tank sizes.
FAQ
Can I use regular home silicone to seal an aquarium?
No. Most household silicones contain mildewcides or fungicides that are toxic to fish even in trace amounts. Only use products labeled as 100% silicone with no additives, or specifically labeled as aquarium-safe. GE Silicone 1 (original formula) is widely trusted by hobbyists for this purpose.
How thick should glass be for a 55-gallon aquarium?
A standard 55-gallon aquarium (48 x 12 x 21 inches) uses 1/4-inch (6mm) glass on the sides and a slightly thicker bottom panel at 3/8 inch in some builds. If you are sourcing your own glass, confirm with a thickness calculator designed for aquarium use and specify your exact dimensions, since the 12-inch width of a 55-gallon makes it relatively safe at 1/4 inch even at that height.
How long does silicone need to cure before I can fill the tank?
A minimum of 72 hours at room temperature (around 70°F) for a complete cure. Some builders wait a full week for large tanks. Temperature affects cure time: silicone cures faster in warm conditions and slower in cold ones. Do not rush this step. Filling before full cure compromises the bond strength.
Is it cheaper to build or buy an aquarium?
For standard sizes, buying a commercial tank is usually cheaper than building one when you account for glass or acrylic cost, tools, and your time. Custom builds make sense when you need a non-standard shape, a very large tank (over 150 gallons), or a specific design like a peninsula or room divider configuration that commercial tanks do not offer. DIY sumps and refugiums are almost always cost-effective since they do not need the same optical clarity as a display tank.
Final Note on Safety
The most important thing to check after assembling any aquarium is that all structural silicone joints are fully cured and the tank does not leak before it goes on a stand in your home. A 55-gallon tank holds 458 pounds of water. A failure is not just an inconvenience, it is a significant floor and furniture disaster. Leak test every tank before placing it permanently, and inspect silicone seals on used tanks before trusting them with your fish.