Why Water Circulation Matters

In the ocean, marine life is constantly exposed to water movement created by tides, waves, and currents.

Inside an aquarium, this movement must be recreated artificially using pumps and wavemakers.

Proper circulation helps:

• Deliver oxygen throughout the aquarium
• Prevent dead spots where waste accumulates
• Keep detritus suspended for filtration removal
• Transport nutrients to corals
• Remove waste from coral surfaces
• Stabilise water parameters
• Improve fish health and activity

Without adequate flow, even a well-filtered aquarium can suffer from algae outbreaks, poor coral growth, and declining water quality.

What Is Water Turnover?

Water turnover refers to how many times the aquarium’s volume is moved every hour.

For example:

• 200-litre aquarium
• Total pump output = 4,000 litres per hour

Turnover rate:

4,000 ÷ 200 = 20x per hour

Different aquarium types require different levels of circulation.

Aquarium Type	Recommended Turnover
Fish Only Marine	10-20x per hour
Soft Coral Reef	20-30x per hour
Mixed Reef	30-50x per hour
SPS Reef	50-100x+ per hour

 

These figures include wavemakers and circulation pumps, not just return pumps.

The Different Types of Water Movement Equipment

Return Pumps

A return pump moves water from the sump back into the display aquarium.

Its primary role is circulation between the tank and filtration system.

Benefits

✔ Powers sump filtration

✔ Increases oxygenation

✔ Maintains water movement

✔ Supports skimmers and reactors

Important Note

Return pumps alone rarely provide enough circulation for a reef aquarium.

Additional flow pumps are usually required.

Powerheads

Powerheads are compact pumps positioned inside the aquarium.

They create directional water movement and improve overall circulation.

Benefits

✔ Simple installation

✔ Adjustable positioning

✔ Affordable

✔ Effective for fish-only systems

Many modern powerheads also include controllable flow patterns.

Wavemakers

Wavemakers are specialised circulation pumps designed to create more natural flow patterns.

Rather than producing a constant stream of water, they vary speed and direction to simulate ocean currents.

Benefits

✔ Natural water movement

✔ Improved coral health

✔ Reduced dead spots

✔ Better detritus suspension

✔ Enhanced reef appearance

Popular manufacturers include:

• Ecotech Marine
• Maxspect
• AI
• Tunze
• Red Sea
• Jecod

Understanding Flow Patterns

Not all water movement is equal.

The goal is to create varied, random flow rather than a constant jet of water.

Laminar Flow

Laminar flow moves in a single direction.

Advantages

• Good for fish-only systems
• Simple to create

Disadvantages

• Can create dead spots
• Less natural for corals
• May cause tissue damage if too direct

Random Flow

Random flow changes direction and intensity.

This closely replicates natural reef environments.

Benefits

✔ Better coral growth

✔ Improved nutrient transport

✔ Reduced debris build-up

✔ More natural conditions

Most modern reef aquariums aim for random flow patterns.

Gyre Flow

Gyre flow creates a circular movement around the aquarium.

Water travels around the entire tank in a continuous loop.

Benefits

✔ Excellent coverage

✔ Fewer dead spots

✔ Efficient debris removal

✔ Ideal for larger aquariums

Gyre pumps are specifically designed to create this effect.

What Are Dead Spots?

Dead spots are areas where water movement is minimal.

These areas often collect:

• Fish waste
• Uneaten food
• Detritus
• Organic debris

Dead spots can lead to:

• Elevated nutrients
• Algae outbreaks
• Cyanobacteria growth
• Poor water quality

Common locations include:

• Behind rockwork
• Tank corners
• Under large coral colonies
• Behind equipment

Good pump placement helps eliminate these areas.

Water Flow and Coral Health

Different coral species require different flow conditions.

Soft Corals

Examples:

• Leather corals
• Mushrooms
• Zoanthids

Preferred flow:

Moderate, indirect movement

Too much flow can prevent polyps from opening fully.

LPS Corals

Examples:

• Euphyllia
• Acanthastrea
• Blastomussa

Preferred flow:

Moderate, turbulent flow

Avoid direct streams that can damage fleshy tissue.

SPS Corals

Examples:

• Acropora
• Montipora
• Stylophora

Preferred flow:

Strong, random flow

High-energy water movement helps remove waste and deliver nutrients.

Positioning Wavemakers Correctly

Pump placement is often more important than pump size.

General Guidelines

• Aim pumps across the tank rather than directly at corals
• Use opposing pumps where possible
• Create intersecting flow patterns
• Ensure water movement reaches behind rockwork
• Observe detritus accumulation and adjust accordingly

A pair of smaller pumps is often more effective than a single powerful unit.

Signs You Need More Flow

Your aquarium may require additional circulation if you notice:

• Detritus collecting on the substrate
• Cyanobacteria outbreaks
• Excessive algae growth
• Coral tissue recession
• Low oxygen levels
• Poor coral polyp extension

Improving circulation often solves these issues without additional filtration equipment.

Signs of Too Much Flow

Excessive circulation can also cause problems.

Watch for:

• Corals remaining closed
• Sandstorms
• Exposed coral skeletons
• Fish struggling to swim normally
• Tissue damage on LPS corals

The goal is strong but controlled water movement.

Choosing the Right Water Circulation Setup

Nano Reef Aquariums (Up to 100 Litres)

Recommended:

• 1–2 small wavemakers
• 20–40x turnover

Mixed Reef Aquariums (100–400 Litres)

Recommended:

• Two controllable wavemakers
• 30–50x turnover

SPS-Dominated Reefs (400 Litres+)

Recommended:

• Multiple high-output pumps
• Gyre systems
• 50–100x turnover

Maintenance of Circulation Equipment

Pumps gradually lose performance due to calcium deposits and debris accumulation.

Regular maintenance should include:

• Cleaning impellers
• Removing coralline algae
• Checking bearings and bushings
• Inspecting cables and controllers

Most circulation pumps benefit from cleaning every 1–3 months.

Final Thoughts

Water circulation is often called the “hidden filtration system” of a marine aquarium. While it doesn’t physically remove waste, effective water movement ensures that filtration equipment can perform at its best while creating the conditions corals and fish need to thrive.

By combining the correct turnover rate, pump placement, and flow patterns, you can create a healthier, more stable marine aquarium with improved coral growth, reduced algae problems, and better overall livestock health.

Need Help Choosing the Right Wavemaker or Circulation Pump?

At Charterhouse Aquatics, we stock a wide range of marine circulation equipment from leading brands including Ecotech Marine, Maxspect, Red Sea, Tunze, AI and Jecod. Our marine specialists can help you select the ideal flow solution for your aquarium size and livestock requirements.

Aquarium Type Recommended Turnover Fish Only Marine 10-20x per hour Soft Coral Reef 20-30x per hour Mixed Reef 30-50x per hour SPS Reef 50-100x+ per hour