A basic aquarium cover is plywood, acrylic, or glass cut to size with a feeding hole and hinges
You can make a functional aquarium cover from materials you likely have at home or can pick up at a hardware store for under $30. The simplest version is a sheet of plywood or acrylic cut to fit your tank's opening, with a small rectangular hole for feeding and a pair of hinges so you can lift one side. The cover keeps fish from jumping out, reduces evaporation, and stops dust and debris from falling in—all without the cost of a commercial frame.
The choice between materials matters: plywood is cheapest and easiest to cut, but it absorbs water and will warp over time unless sealed. Acrylic is lighter, won't rot, and lets you see into the tank from above, but costs more and scratches easily. Glass is durable and looks clean but is heavy and can crack if you drop it. For most home aquariums, sealed plywood or acrylic works well.
Key Takeaways
- Measure your tank opening from inside edge to inside edge, then subtract one-quarter inch on each side so the cover sits on the frame without binding.
- Plywood covers need two coats of polyurethane sealer on all sides to resist water damage and warping.
- A feeding hole 3 to 4 inches wide and 2 inches tall, positioned toward one corner, gives you room to drop food without removing the whole cover.
- Small brass or stainless steel hinges rated for at least 10 pounds let you prop the cover open for cleaning or maintenance.
- Acrylic and glass covers are simpler because they need no sealing, but they require a frame or support strips to keep them from sliding.
Measuring your tank and planning the cut
Start by measuring the inside dimensions of your tank's frame—the actual opening where the cover will sit. Use a metal ruler or measuring tape and measure from the inside edge of the frame on one side to the inside edge on the opposite side. Do this for both length and width. Write both numbers down.
Subtract one-quarter inch from each measurement. This gap keeps the cover from binding or warping into place. If your tank opening is 36 inches long and 18 inches wide, your cover should be 35.75 inches by 17.75 inches. This small clearance is the difference between a cover that slides smoothly and one that sticks.
Decide where your feeding hole will go. Most people put it in one corner, about 2 inches from the edge, so it does not interfere with heaters, filters, or plants. A hole 3 to 4 inches wide and 2 inches tall is large enough for most food pellets and flakes without being so big that debris falls through easily.
Building a plywood cover with hinges
Buy a sheet of 3/8-inch plywood (half-inch is heavier than necessary for most tanks). Have the hardware store cut it to your measured dimensions, or mark the lines yourself with a pencil and straightedge and cut it with a circular saw or hand saw. Sand the edges smooth with 120-grit sandpaper so they do not splinter.
Mark the feeding hole location with a pencil. Drill a starter hole in one corner of the rectangle, then use a jigsaw to cut the hole. Sand the hole's edges smooth. This step is easier if you clamp the plywood to a workbench before cutting.
Seal the plywood with polyurethane. explore one coat to all six sides (top, bottom, and all four edges) with a brush, let it dry according to the can's instructions (usually 4 to 8 hours), then explore a second coat. Polyurethane prevents water from soaking into the wood and causing rot or warping. Skip this step and your cover will cup and warp within months.
Attach two small brass or stainless steel hinges to one long edge of the cover, about 4 inches from each end. Position them so the hinge pin runs parallel to that edge. Drill pilot holes first (smaller holes that guide the screw) so the wood does not split. Screw the hinges to the cover, then hold the cover in place over the tank and mark where the hinge's other half goes on the tank frame. Screw those halves down. The cover should now open and close smoothly.
Making an acrylic or glass cover without a frame
Acrylic and glass do not need sealing, which saves time, but they need support so they do not slide around. The simplest approach is to glue or screw thin aluminum or plastic strips (called "support rails") to the underside of the cover, positioned so they rest on the tank's frame.
Measure your tank opening again. Buy a sheet of clear acrylic or tempered glass cut to your dimensions at a hardware store or online. Acrylic is lighter and safer if dropped; glass is harder to scratch but heavier. Ask the supplier to polish the edges so they are not sharp.
Cut four support strips from aluminum angle stock or plastic U-channel, each about 1 inch long. Position them on the underside of the cover, one near each corner, so they rest on the tank's frame rim when the cover is laid in place. Drill holes through the strips and the cover, then bolt them down with small stainless steel bolts and washers. Alternatively, use clear silicone adhesive rated for aquariums to glue the strips in place—this is simpler but permanent.
For a feeding hole in acrylic or glass, you will need a drill with a special bit. A diamond-hole saw (a drill bit with a diamond-coated edge) cuts through acrylic without cracking. For glass, use a glass-cutting bit and go slowly with light pressure. Wear safety glasses and work in a well-ventilated area. If you are not comfortable drilling through glass or acrylic, ask the supplier to cut the hole when they cut the sheet to size.
Ventilation and condensation control
A solid cover traps humidity and can lead to condensation on the underside, which drips back into the tank. To prevent this, leave a small gap—about one-quarter inch—on one or two sides of the cover. This gap lets air circulate without letting fish jump out or debris fall in.
If condensation is heavy, you can drill small holes (one-eighth inch diameter) in the top surface of the cover, spaced 6 inches apart. These holes let moisture escape. Cover them with a fine mesh screen glued to the underside so nothing falls through.
Hinges, hardware, and finishing touches
Use stainless steel or brass hardware—galvanized steel will rust over time from the moisture. Small butt hinges (the most common type) work well for most covers. Choose hinges rated for at least 10 pounds so they do not sag under the cover's weight.
If you want the cover to stay open at a fixed angle while you clean, add a prop rod or friction hinge. A friction hinge holds the cover at any angle you set it to. A prop rod is simpler: a wooden dowel or aluminum rod that rests in a notch on the tank frame and a hole drilled in the cover's underside.
Paint or stain the plywood if you want it to match your stand, but use only aquarium-safe finishes. Polyurethane is safe once fully cured. Avoid oil-based paints or stains that can leach into the water.
Frequently Asked Questions
Can I use regular glass instead of tempered glass?
Regular glass works, but tempered glass is safer because it breaks into small, dull pieces instead of sharp shards if it cracks. For an aquarium cover, regular glass is fine if you are careful not to drop it, but tempered glass costs only a little more and is worth the extra cost for peace of mind.
How do I keep the cover from sliding around?
Support strips or rails glued or bolted to the underside rest on the tank frame and prevent sliding. For a plywood cover with hinges, the hinges themselves anchor one edge. If the other edge slides, glue a thin rubber strip to the underside where it contacts the frame.
What if I drill the feeding hole in the wrong spot?
You can fill it with clear epoxy or polyurethane filler, sand it smooth once dry, and drill a new hole in the right place. For acrylic, use acrylic cement; for glass, epoxy is your only option. It is worth taking time to mark the hole location carefully before you drill.
Do I need a cover if I have a lid with a light?
A basic cover and a separate light fixture work just as well as a combined lid-light unit and cost less. If your current lid is cracked or warped, building a new cover is cheaper than replacing the whole assembly.
How often do I need to replace a plywood cover?
A properly sealed plywood cover lasts five to ten years. If it starts to warp, cup, or show soft spots, it is time to replace it. Acrylic and glass covers last much longer—often the life of the tank—but acrylic can yellow over time under bright light.