The amount of flow your reef needs depends on its size and the corals you keep. Soft corals generally prefer gentler movement, LPS corals benefit from moderate, indirect flow, while SPS corals typically need stronger, more turbulent currents.

As a rough guide, here's how much combined wavemaker flow you might need:

50 litre aquarium

• Soft corals: 500–1,000 L/h
• Mixed reef: 1,250–2,000 L/h
• SPS reef: 2,000–3,000 L/h

100 litre aquarium

• Soft corals: 1,000–2,000 L/h
• Mixed reef: 2,500–4,000 L/h
• SPS reef: 4,000–6,000 L/h

200 litre aquarium

• Soft corals: 2,000–4,000 L/h
• Mixed reef: 5,000–8,000 L/h
• SPS reef: 8,000–12,000 L/h

300 litre aquarium

• Soft corals: 3,000–6,000 L/h
• Mixed reef: 7,500–12,000 L/h
• SPS reef: 12,000–18,000 L/h

500 litre aquarium

• Soft corals: 5,000–10,000 L/h
• Mixed reef: 12,500–20,000 L/h
• SPS reef: 20,000–30,000 L/h

These figures are starting points rather than strict rules. The shape of your aquarium, your rockwork and the positioning of your wavemakers all influence how water moves. The aim is to keep water circulating throughout the aquarium without blasting your corals or allowing waste to collect in dead spots.

our return pump moves water from your sump or filtration compartment back into your aquarium. Unlike wavemakers, which create movement around the display, a return pump's main job is to circulate water through your filtration system.

For most marine aquariums with a sump, a good starting point is around 3–5 times your display aquarium's volume per hour.

Here's a rough guide to the actual flow you should aim for:

• 50 litre aquarium: 150–250 L/h
• 100 litre aquarium: 300–500 L/h
• 200 litre aquarium: 600–1,000 L/h
• 300 litre aquarium: 900–1,500 L/h
• 500 litre aquarium: 1,500–2,500 L/h

Remember, a return pump's advertised flow rate is usually measured with little or no resistance. As water travels upwards through pipes, bends and fittings, the actual flow decreases.

For example, a pump advertised at 3,000 L/h might deliver considerably less once installed beneath your aquarium. Always check the manufacturer's flow chart at your required pumping height.

The number of wavemakers you need depends on your tank's size, shape, rockwork and the corals you're keeping.

As a general starting point:

• Nano reefs (up to 100 litres): One adjustable wavemaker may provide sufficient circulation.
• Small reefs (100–200 litres): One or two wavemakers, depending on their output and positioning.
• Medium reefs (200–400 litres): Two wavemakers are often beneficial for creating varied flow and reducing dead spots.
• Large reefs (400 litres and above): Two or more wavemakers may be needed to provide circulation throughout the aquarium.

Having more wavemakers doesn't necessarily mean stronger flow. Two pumps running at lower settings can sometimes create better water movement than a single powerful pump.

Position your wavemakers to create broad, indirect currents rather than pointing them directly at your corals. Watch for areas where debris settles, as these can indicate poor circulation.

Ultimately, the goal is to create natural, varied water movement that reaches all areas of your reef.