How to Build an Aquarium Lid: DIY Fish Tank Screen Top

An aquarium screen top is built from three standard parts you can buy at any hardware store: aluminum window screen frame stock, screen spline, and mesh. TankRig wrote this guide because tank makers publish the outside of a tank but never the inside of its rim, so a real build starts with measuring your own tank instead of reading a number off a chart.

Below is the parts list, a table of how much stock to buy for nine common tank sizes, a plain look at the mesh choices, and the cut and assemble steps. Every tank footprint here comes from Aqueon's own dimension table rather than a rounded size chart.

Why do fishkeepers put a screen top on a tank?

Keepers use a screen top for two reasons: some fish jump, and open water evaporates. A screen top is a mesh panel in a frame, so it covers the water while air and light still pass through. TankRig will not tell you a screen top will keep any animal in your tank, and we do not give an evaporation number. Read both of those as reasons keepers build these, not as results we promise.

A screen top is not the same thing as a glass lid or a hood. Glass sits right on the water and traps warm damp air under it. Mesh lets air move. Keepers with strong lights often pick mesh because it does not fog, does not drip, and does not sit between the light and the water as a solid sheet.

The other reason people build instead of buy is simple. Store lids come in a handful of sizes. If your tank is rimless, or an odd size, or you cut a hole for a hang on back filter, there is often nothing on the shelf that fits. Frame stock comes in long lengths and you cut it to whatever you have.

What is an aquarium screen top made of?

A screen top is four pieces of frame stock, four corners, one piece of mesh, and one length of spline. That is the whole parts list, and every piece of it is a standard window screen part sold by the foot or by the roll.

Here is what each part does.

• Aluminum frame stock. Thin folded aluminum with a groove down one face. Sold by thickness and face width, like 5/16 by 3/4 inch. The 5/16 by 3/4 size is the common one and the cheapest.
• Corners. Small plastic or metal pieces that join two cut ends into a 90 degree corner. There are two kinds and they are not swappable. One kind wants square cut ends. The other kind wants 45 degree cuts. Pick your corners before you cut anything.
• Mesh. The screen itself. Fiberglass, aluminum, tough polyester, or solar screen. This is the choice that matters most, and the next section covers it.
• Spline. A round rubber cord that you press into the groove to trap the mesh. Sold by diameter in thousandths of an inch, like .125 or .140.
• A spline roller. A small wheel tool, usually a few dollars. You can force spline in with a butter knife, but you will cut the mesh doing it.
• A hacksaw or a small miter box, and a utility knife for trimming.

What size spline do you need?

Match the spline to your frame stock and to your mesh, and buy both from the same place if you can. The table below is Phifer's own published guide, but TankRig has to flag something on it right away: a second big supplier publishes completely different numbers for the same frame size, so treat this table as a starting point and check what your own stock takes.

Thicker mesh needs a thinner spline, which feels backwards until you think about it. The mesh folds down into the groove on both sides of the spline, so a thick mesh already fills part of the channel.

Which mesh should you use for a fish tank lid?

For most tanks, standard fiberglass insect screen is the right pick, because it is the most open mesh sold and it is the easiest to roll in. TankRig is calling that from the published openness figures below rather than from testing over a tank, so if your tank is heavily planted or is a reef, understand that every mesh takes some light and none of these numbers were measured under an aquarium light.

The trade is openness against toughness. The tougher a mesh is, the thicker its strands are, and thicker strands mean less light and less air. Pet screen and solar screen are much stronger and much darker.

How much frame stock and mesh do you need for your tank?

Use the table below to buy, not to cut. TankRig built these amounts from Aqueon's published outside tank footprints with waste added, so they tell you how much to put in the cart, and they are deliberately a little generous. They are not cut lengths, because no tank maker publishes the inside of the plastic rim your frame has to fit into.

If your tank is rimless, the frame sits on the glass instead of inside a rim, so the numbers come off the outside of the glass. Either way, take your own numbers before you cut.

How do you size a screen top to your tank?

Size the frame to the opening you are actually filling, not to the tank. This one surprises people: no aquarium maker publishes the inside opening of a rimmed tank's plastic top rim, so there is no chart anywhere that can hand you a cut length. The shops selling glass lids work the same way.

On a rimmed tank, put a tape inside the plastic rim and read the clear opening, front to back and side to side. Write both numbers down. The rim eats roughly an inch off the published outside length, but that number moves by tank and by maker, so it is a sanity check and never a cut length.

On a rimless tank, go by the outside of the glass, because your frame will sit on top of the glass rather than inside anything. Note the glass thickness too if you plan to use edge clips. Rimless tanks are almost always 5, 6, 8, 10, or 12 mm glass, and the brands that publish a number never publish anything in between those steps.

Then decide how the top sits before you cut. There are three normal answers, and they change your cut length: dropped inside the rim, resting on top of the rim, or held on the glass edge with clips.

How do you build an aquarium screen top, step by step?

The build is nine steps and the only step people rush is the first one. TankRig lists a test corner as its own step below on purpose, because how much length a corner eats depends on which corner style you bought, and cutting all eight ends before you know that number is the usual way a first build gets thrown away.

1. Read your opening, or the outside of your glass on a rimless tank. Write down both numbers.
2. Pick your corner style. Square cut corners press into square cut ends. Miter corners need 45 degree cuts. They are not swappable, so choose now.
3. Cut one test corner. Join two scrap ends with one corner and measure how much total length the corner adds or eats. That one number is what you subtract from your opening.
4. Cut your four pieces with a hacksaw or a small miter box. Go slowly. Aluminum this thin will crush if you clamp it hard, so pad the vise.
5. Dry fit the frame with the corners pushed in and no mesh. Set it on the tank and check it before you go any further.
6. Lay the mesh over the frame with two or three inches hanging over on all sides. Keep it square to the frame.
7. Roll the spline in with a spline roller. Do one long side first, then the opposite long side, then the two ends. Keep light tension only. Pulling it drum tight will bow the frame in.
8. Trim the extra mesh with a utility knife, running the blade along the outside edge of the spline. A fresh blade cuts, a dull blade drags the mesh out.
9. Set it on the tank, mark where cords and hoses need to pass, and add clips or hooks if the top slides around.

What about long tanks with a center brace?

Standard 55 and 75 gallon rimmed tanks have a plastic brace across the middle of the top, and it changes the build. TankRig would rather tell you the easy answer than sell you extra parts: on most 48 inch tanks, building two smaller screen tops that meet over the brace is easier than building one big one, and it uses about the same amount of stock.

The reason is that a 48 inch span of thin aluminum sags in the middle. One long top either needs a support bar running across the middle, or it needs to arch over the factory brace without rocking on it. Two half tops just rest on either side of the brace and each one is short enough to stay flat.

If you do want one piece, plan a middle support. Run a fifth length of frame stock across the short direction at the middle of the top and join it with a T fitting. Buy about another 13 inches of stock for a 55, or about another 19 inches for a 75, plus a little waste.

One more thing on long tops. Two smaller panels are much easier to lift off one handed at feeding time, and easier to store when they come off.

Where do printed parts help on a screen top?

Three spots on this build are where a hardware store kit runs out, and all three are small parts rather than the frame itself. TankRig is working on printed hardware for exactly these three spots, and to be straight with you, none of it is for sale yet, so treat this section as the honest list of what is annoying about the standard build rather than as a pitch.

The corner is the first spot. The molded corner that comes in a kit hides inside the frame and holds by friction against a thin folded shell, and it is generic across every use of screen frame in the world. A corner made for an aquarium can grip the outside of the frame instead, and it can carry a mount for a clip or a hook that a hidden corner cannot.

Holding the top on the tank is the second spot. A rimmed tank and a rimless tank need completely different answers, and neither one comes in the box. A rimmed tank wants a clip that catches the plastic rim. A rimless tank wants a hook that grips the glass edge, which has to open across the whole 5 to 12 mm range that rimless tanks are actually built in.

Openings are the third spot, and they are the reason most home built tops end up with a chopstick under one corner. You need a way to feed without pulling the whole top off, and you need cords and hoses to pass through without leaving a gap. A hatch that clamps the mesh, and a corner with a notch and a cap for cords, both solve that better than cutting a hole and hoping.

Until those parts exist, the standard build works, and this guide is written so you can finish one today with parts from a hardware store.

Frequently asked questions