Filter & Watercourse Pumps

You need two numbers: the head height (how high the water has to be lifted) and the flow rate (how much water you want at the top).

1. Measure the height from the water surface in the pond or reservoir to the highest outlet. This is your head height.
2. Work out the flow you want for the job (see the waterfall and bubbling stone questions below, or use the pond volume guide for filter-pump sizing).
3. Check the pump's performance: the flow printed on the box is at zero height, so the flow you actually get at your head height is always lower.

Pick a pump that sits comfortably in the middle of its range at your head height. A slightly bigger pump you can turn down is better than a small one running flat out. If you're unsure, email us the measurements and we'll suggest a pump.

Pond volume decides what size filter, UV clarifier and pump you need, so it's worth getting right. Metric is easier.

Rectangular or square ponds: length × width × average depth (in metres) × 1,000 = litres.

A pond 3 m × 2 m × 0.6 m deep is 3 × 2 × 0.6 × 1,000 = 3,600 litres.

Round ponds: 3.14 × radius × radius × depth (in metres) × 1,000 = litres. The radius is half the width across.

A round pond 2 m across and 0.6 m deep is 3.14 × 1 × 1 × 0.6 × 1,000 = 1,884 litres.

Irregular or kidney shapes: work out the volume as if it were a rectangle around the pond, then take off about a third. Easier method: fill the pond with a hose and time it. If your hose fills a 10-litre bucket in 1 minute and takes 40 minutes to fill the pond, the pond holds about 400 litres.

Use the average depth, not the deepest point, unless the sides are vertical. If you have fish, round up when sizing filters: more capacity is always better than less.

It depends on what the water is doing:

The key practical difference: fountain pumps have small intake holes to keep nozzles clear, while filter and watercourse pumps have large intake cages so debris passes through to the filter.

Browse feature pumps, fountain pumps or filter & watercourse pumps.

OASE's rule of thumb is based on the width of the spillway lip:

• Gentle trickle: about 100 l/h for every cm of width
• Lively flow: about 200 l/h for every cm of width

A 20 cm lip needs roughly 2,000 l/h for a gentle flow, or 4,000 l/h for a lively one, at your head height, not open flow. The length of the stream doesn't change the pump size; once the water's at the top, gravity does the rest. Each OASE waterfall page also lists the pump size OASE recommends for it.

All three are filter and watercourse pumps, built to run continuously and feed filters, streams or waterfalls. They differ in size and in how you control the flow.

Short version: Eco Premium is the best all-rounder for most garden ponds. Eco Expert is for big ponds and powerful waterfalls where you need serious flow. Eco Twin gives you two motors you can run separately, so one pump covers quiet and busy seasons.

Browse the full filter & watercourse pump range. Unsure which model? Email us the pond volume and waterfall height and we'll pick the right one.

For a fish pond, yes: keep the filter pump running. Moving water is slower to freeze, keeps oxygen levels up, and keeps the biological bacteria in the filter alive. Several OASE pumps, including the AquaMax Eco Premium, are frost-proof down to −20 °C.

Raise the pump off the bottom in winter (put it on a brick or move it to a shelf) so it doesn't stir up the warmer water at the bottom where fish rest.

Fountains and decorative water features are different. Switch them off before hard frost. Ice can crack nozzles and pipework, and the spray cools the pond faster than it needs to.

Wildlife ponds with no fish can be shut down for winter if you prefer. If the pond fully freezes, make a hole in the ice by resting a saucepan of hot water on the surface. Never smash the ice, as the shockwave can harm fish.