Standard vs cat-proof aquarium lids and evaporation covers

What is the difference between a standard polycarbonate mesh lid and a cat-proof lid? And do evaporation covers make a standard lid cat-proof? These are questions we hear regularly, because the options can look similar until you see how they are built.

There are two separate choices: the construction of the lid, and whether to add evaporation covers. Both our standard and cat-proof designs can be used with covers.

The standard polycarbonate mesh lid

Our standard lid has a clear polycarbonate frame with fine mesh spanning the open sections. The frame is shaped around the aquarium and its equipment, with cutouts and feeding access agreed in the artwork.

The mesh helps keep fish inside the tank while leaving the surface open to air. It is glued into the lid for a stronger hold and to reduce the chance of it loosening or coming out. It is not a replaceable mesh insert.

What changes with the cat-proof option?

The cat-proof design adds a rigid polycarbonate section with hexagonal openings across the mesh area. Fine mesh remains beneath the hexagonal section.

This gives the lid additional support across areas that would otherwise be a large span of mesh. The photograph below shows the hexagonal structure that distinguishes the cat-proof design.

If cats can reach the top of your aquarium, choose the cat-proof option when ordering and tell us about your setup. The standard mesh design and the cat-proof design have different constructions; adding an evaporation cover does not add the cat-proof hexagonal reinforcement.

Where evaporation covers fit in

Evaporation covers are removable, solid 4 mm clear polycarbonate panels. They cover the open sections to help reduce water loss. They are an optional addition to either lid type.

• On a standard lid: the covers sit over the mesh sections.
• On a cat-proof lid: the cover goes over the hexagonal section.

The covers have a supporting lip so they sit within the mesh well while resting on the surrounding lid. They are made to fit the lid rather than simply being a loose sheet placed across the aquarium.

The two options do different jobs: the cat-proof structure provides additional rigid support, while evaporation covers help reduce water loss. You can choose either, both, or a standard mesh lid without covers.

The four combinations at a glance

Using evaporation covers on a reef tank

Open mesh should not be expected to stop evaporation. Solid covers can reduce it, but changing surface coverage also changes ventilation and heat retention. Keep an eye on temperature and the aquarium’s response after fitting or removing covers.

Water loss will vary with the room, equipment and amount of surface covered, so there is no single reduction percentage that suits every tank. Continue checking water level and salinity, and review your top-up routine when evaporation changes. Our evaporation and top-up guide explains this in more detail.

Choosing the right lid for your aquarium

Start with the lid construction you need, then decide whether evaporation covers would help your setup. Include light mounts, cables and feeding access in your order details. We will confirm the measurements and cutout positions with you and send visual artwork for approval before manufacture.

For a Red Sea, Waterbox, D-D or another listed aquarium, find your tank’s model-specific lid. For a custom-built or non-standard aquarium, use our custom-built aquarium lid builder.

Production takes 10–15 working days from artwork approval. You can find more about ordering, lid materials and care in our FAQs, or email info@londonaquaticdesign.co.uk if you need help choosing.