Two ways to the same goal
Both a home-made screen top and a custom-cut lid keep fish in while the tank breathes. One costs an evening and a trip to the hardware store, the other costs more and arrives in a box. This page is a fair account of what each one is good at, written by a company that sells the second kind. If a DIY screen is right for your tank, you should build one.
The DIY screen top
The standard build is a window-screen frame kit: aluminum or vinyl channel cut to length, four plastic corners, a roll of mesh and a rubber spline pressed in with a roller. Reef suppliers sell kits with a clear or white netting instead of dark window screen, which shades the tank less. An hour of work, a hacksaw or a miter box, and the top is done.
Where it works well
- Cost. A kit and mesh is the cheapest cover you can put on a tank.
- Framed tanks. A plastic rim has an inner ledge the frame can sit in, so it stays put and sits flush.
- Gas exchange and light. With a clear mesh, a screen top is as open as a tank can be and still be covered.
- Odd shapes. A frame can be built around a brace or a bracket by cutting and joining more pieces.
Where it falls short
- Rimless tanks. There is no ledge, so the frame sits on the bare top edge of the glass. It slides when touched, leaves a slot along every edge for a goby or a shrimp, and a frame built a little small falls in.
- Sag. Spline-held mesh loosens over time and the frame channel bows across a wide tank, so the middle droops toward the water.
- Feeding. The whole frame lifts every time you feed, which is when fish are at the surface and excited. Cutting a feeding hole in spline mesh is possible but ragged.
- Cords and brackets. A light arm or a hang-on filter means a notch in the frame or a corner left open. Open corners are where fish go.
- Looks. Aluminum channel and corners on a rimless, low-iron tank undo the reason the tank was bought.
- Ageing. Salt creep corrodes aluminum, the plastic corners get brittle under the light, and the mesh is usually replaced within a couple of years.
The custom polycarbonate lid
A MasterLids lid is a single sheet of 3/8-inch clear polycarbonate cut on a CNC to the outside of your tank's glass, with a mesh window in the middle and a lip underneath that sits inside the glass. There is no frame to assemble; the sheet is the frame. Catalog lids are drawn for 180+ production tanks, and the custom builder takes three measurements for anything else.
Where it is better
- Fit on a rimless tank. The lip inside the glass means it cannot slide, and the outer edge lines up with the outside of the tank. The corners are closed.
- Rigid. 3/8-inch polycarbonate does not sag or bow, and the mesh is held in a machined window rather than a spline.
- Feeding hole with a cap. Placed where you feed, so the lid stays on. A feeding cup that holds food at the surface is an option.
- Cutouts drawn in. A notch for a light bracket, a cord or a hang-on filter is a line on the drawing, sized to what passes through it, with clearance.
- Evaporation cover. A clear panel that snaps over the mesh when you want the top sealed, and comes off when you do not.
- Proof before cutting. You see the lid with every hole and cutout and approve it before anything is made. Catalog lids are guaranteed to fit the model, and a lid that does not fit because of our error is remade free.
- Looks. Clear polycarbonate on a rimless tank is nearly invisible from the front.
Where the DIY screen still wins
- Price. A custom lid costs more than a kit. On a cheap framed tank the screen is the sensible choice.
- Framed tanks. We do not build for plastic-rimmed tanks; a lip inside the glass is the wrong design for a rim with its own ledge.
- Today. A screen can be on the tank tonight. A lid ships within about a week of the proof being approved, and usually faster than that.
Side by side
| DIY screen top | Custom polycarbonate lid | |
|---|---|---|
| Cost | Lowest | Higher; priced per model on the product page |
| Time to a covered tank | Tonight | About a week after you approve the proof |
| Fit on a rimless tank | Rests on the glass edge, can slide or fall in | Lip sits inside the glass; cannot slide |
| Fit on a framed tank | Sits in the rim ledge; good | Not offered |
| Gaps at the corners | Usually some | Closed |
| Feeding | Lift the frame | Capped feeding hole where you feed |
| Cords, brackets, filters | Notch the frame or leave a corner open | Cutouts sized to each item, on the proof |
| Sag over time | Mesh loosens, channel bows | None at 3/8-inch |
| Evaporation control | None | Optional snap-on cover |
| Looks on a rimless tank | Visible aluminum frame | Clear, nearly invisible |
| Lifespan | Mesh and corners replaced every few years | Polycarbonate frame lasts; mesh window can be renewed |
If you go custom
Start by looking for your tank in the catalog; if it is there, nothing needs measuring. If it is not, three outside measurements are enough to draw it in the builder, and the cutout guide covers anything that crosses the glass.