Not every marine aquarium needs a protein skimmer, but they can make maintaining water quality considerably easier.

Protein skimmers remove organic waste from aquarium water before much of it breaks down into ammonia, nitrate and phosphate. They're particularly useful in heavily stocked aquariums, systems with regular feeding and larger reef tanks.

Smaller marine aquariums can often run successfully without a skimmer, relying on biological filtration, mechanical filtration and regular water changes instead.

A protein skimmer can also help improve gas exchange, supporting oxygen levels in your aquarium.

Protein skimmers are usually rated according to aquarium volume, but the number of fish and how heavily you feed can be just as important.

As a rough guide:

• Lightly stocked aquarium: A skimmer rated for approximately your aquarium's total water volume.
• Moderately stocked aquarium: A skimmer rated for around 1.5 times your total water volume.
• Heavily stocked aquarium: A skimmer rated for up to twice your total water volume may be appropriate.

For example, a 300-litre reef aquarium with moderate stocking might benefit from a protein skimmer rated for approximately 450 litres.

However, skimmer ratings vary considerably between manufacturers. An excessively oversized skimmer may struggle to produce consistent foam, so bigger isn't always better.

Always check the manufacturer's recommended stocking levels and ensure the skimmer fits your sump and operates at the correct water depth.

Both filter socks and automatic filter rollers provide mechanical filtration, capturing uneaten food, fish waste and other particles before they break down in your aquarium.

Filter socks are reusable fabric filters that trap debris as water passes through them. They're simple and effective but need regular cleaning to prevent trapped waste from accumulating.

Automatic filter rollers use a roll of filter fleece that advances when the material becomes clogged. Dirty fleece is gradually replaced with clean material, removing trapped debris from the water flow without needing to wash filter socks.

Both can work well in a marine aquarium. Filter socks are a straightforward option, while automatic rollers can reduce routine maintenance, particularly on larger or heavily stocked systems.