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. However, is it possible your aquarium filter is overly powerful and produces current that is too strong for your fish? Some fish have long and flowy fins, are small in size, or originated from slow-moving waterways and aren’t built to handle torrents of water. Your fish could become stressed from constantly fighting against rapid flow and get whipped around your tank. 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

To reduce current, you can avoid using too much filtration in an 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. Do not be afraid to reduce the size of your filter if your fish seem to be struggling.

Our favorite type of filtration for gentle flow is a sponge filter with a smaller pump like the USB nano air pump. Its coarse foam is ideal for straining any debris from the water and not sucking up any baby fish. The bubbles also create good surface agitation to ensure that your fish get enough oxygen. You can adjust the pressure of an air pump by using a flow dial. If the pump doesn’t have a flow dial, you can add an external valve to reduce bubbling. You may prefer another type of filter such as a hang-on back or canister filter. If the pump has an adjustable knob or switch that allows you to adjust the flow rate of water entering the aquarium, this will be an option.

Sponges provide gentle flow that won’t harm your fish fry, bettas, and other nano fish.

Reduce the Output

There are many ways to baffle, block, or redirect the water flowing out of the filter to reduce the water pressure. To dispel some water pressure in an aquarium that has an internal filter or canister, aim the output towards the surface of the water or against the wall. When the water “bounces” off the surface or wall, it loses kinetic energy and the current decreases. Another option is to place a prefilter sponge over 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. Finally, some canister filters allow you to attach a spray bar to the output so that the water loses energy as it’s dispersed through a row of holes. To lessen the current even more, aim the spray bar holes toward the back wall of the aquarium.

Attach a prefilter sponge or spraybar to the filter output in order to reduce 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. You can cut out a block of sponge that fits the width of the waterfall and stuff it into the waterfall opening. Another idea is to attach craft mesh across the waterfall opening using zip ties or string. Some people recommend attaching a soap dish container with suction cups to the aquarium wall under the waterfall. To dampen the flow, you can add foam, decorative marbles, or moss balls 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. Adding decorations and plants to the aquarium will cause the water to break down and slow down. Depending on the configuration of your aquarium, you might be able to combine multiple of these techniques to lower the current and provide the fish with the stress-free environment they desire.

To reduce the flow, place a soap dish, plants or decorations underneath the waterfall of your hang on-back filter.

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