How to Slow the Flow in Your Aquarium

Previously, we discussed the importance of filtration for fish tanks because it cleans up debris particles, grows beneficial bacteria, and helps create water movement and surface agitation for improved oxygenation. Is it possible that your aquarium filter produces too much current for your fish? Some fish are large and have flowing fins. Others are smaller and were born from slow-moving waters. They are not built to handle high volumes of water. Fighting against the flow of water can lead to fish getting tossed around, hiding in shelters, or developing illnesses. These techniques can be used to decrease the current in your aquarium if you have a betta fish or goldfish, or any other slow-swimming animals.

Use a Filter with Slow Flow

You can reduce current by not using too much filter in your aquarium. People often install multiple filters in an effort to keep their tank clean. Some hobbyists buy an all-in-1 aquarium kit, but don’t realize the default filter is too strong to support bettas and slower fish. Don’t be afraid if you notice your fish are struggling to get the filter downsized to meet their needs.

For gentle flow, our favourite type of filtration is a sponge filter that uses a smaller pump such as the USB Nano air pump. The coarse foam can be used to strain debris out of the water, without sucking up baby fish. Additionally, the bubbles provide good surface agitation so that your fish get enough oxygen. Most air pumps have a flow dial that can be used to lower the pressure. However, if the pump is not adjustable, an air valve can be added to the tank to reduce bubbles. You can also use a different type of filtration such as a hang on-back or canister filter.

Sponges are gentle and won’t cause harm to your fish fry, bettas or other nano fish.

Baffle the Output

To reduce water pressure, there are several ways to block, redirect, or baffle the water coming out of the filter. To reduce water pressure, you can use an aquarium’s internal filter or canister with an output spout. You can aim the output at the aquarium’s water surface or back wall. The current drops if the water “bounces off” the wall or surface. Another idea is to put a prefilter sponge on the output. The coarse sponge will help dissipate most water’s energy and still allow water to enter the fish tank. You can secure the pre filter sponge against a wall, aquarium decoration or other sturdy surface if the water flow is too strong to remove it. A spray bar can be attached to some canister filters to help reduce energy loss when water passes through a row. The spray bar holes should be aimed towards the aquarium’s back wall to reduce the current.

Attach a pre-filter sponge or spray bar onto the filter output to dissipate the water pressure.

There are many filter baffle options that can be used to reduce flow in a hang-on back filter with a waterfall output. Cut a block of sponge to fit the opening of the waterfall. You can also attach craft mesh to the waterfall opening with zip ties or string. Some people recommend attaching a soap dish container with suction cups to the aquarium wall under the waterfall. To further dampen the flow of water, add some foam, marbles, or moss to the soap dish.

Finally, try placing live plants, hardscape, or fish tank ornaments in front of the filter output or underneath the waterfall to help block the force of the water. More plants and decorations added throughout the rest of the aquarium will also break up and hinder the water movement in the tank. Depending on your setup, you may be able to combine several of these methods to decrease the current and give your fish the stress-free environment they need.

Place a soap dish or other decorations under the waterfall of the hang-on-back filter. This will reduce the flow.

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