Choosing a Reef Flow Pump: Output, Tank Walls and Placement

You cannot choose a suitable flow pump from its litres-per-hour rating alone. Start by watching the running aquarium: do polyps move without being constantly pushed to one side? Does debris collect behind the rockwork? Is sand being blown away? These observations help you decide whether to change the direction, distribution or strength of the flow. Then compare pump output and controls.

Check the wall where you will mount it

Check the material and measure the thickness of the wall where the pump will actually sit. Side and rear panels may differ. Check the instructions for the exact pump model to confirm that its mount suits that thickness and glass or acrylic. A specification for a different model is not enough. Ask the aquarium manufacturer if you do not know the panel thickness.

Also check space inside and outside the aquarium for the mount, cable and maintenance access. A magnet trapped behind furniture can make an otherwise useful position awkward. Ask for a missing mounting specification before ordering rather than relying on a guess.

Control matters beyond maximum output

Do not compare maximum ratings alone. What output settings does this particular model offer? Which modes work without extra equipment? Does it need a controller, an app or a specific connection? Check each model separately. Adjustable does not automatically mean finely adjustable or compatible with your existing equipment.

You need a usable operating range for your aquarium. A compact LPS area may call for a lower, finer setting, while a long rock structure presents a different distribution problem. This is why we do not recommend a universal fixed multiple of tank volume here.

Three practical buying situations

• A compact aquarium with fleshy LPS: First check whether the pump can be sufficiently reduced and directed at the intended position. An impressive maximum is of little value if the gentler setting your layout needs is missing.
• A long mixed reef with central rockwork: Sketch obstacles and open water paths. Compare positions that can reach different areas, rather than planning more power along the same route.
• An increasingly dense SPS reef: Plan accessible maintenance positions and room for later adjustments. Growing colonies change the routes through the reef; spare capacity helps only if movement reaches the intended area.

Observe the result after installation

Start at a low setting and change only the position, direction or programme at a time. Watch the same areas afterwards. If long tentacles are constantly flattened, redirect or reduce the flow. If debris remains behind the rockwork, look for a different flow path rather than simply increasing output. Check again over the following days to see how the sand, corals and deposits respond.

Our Torch coral flow guide addresses Euphyllia. For large single polyps, see the Trachyphyllia, Acanthophyllia and Cynarina guide. Coral and pump placement need to work together.

Consider intake protection and maintenance before buying

If you keep anemones, check before buying whether an intake guard is available for the exact pump model. A guard cannot guarantee protection from injury. Inspect it regularly: blocked openings can reduce flow. Clean and fit it according to its instructions.

Follow the model's directions for cleaning and reassembly, then check operation and position. Explore our flow pump collection with five details ready: tank dimensions, livestock, rockwork, wall material and thickness, and your preferred control method.