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. It is possible that your aquarium filter is too powerful and is producing too much current 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. Fighting against the flow of water can lead to fish getting tossed around, hiding in shelters, or developing illnesses. So, if you own a betta fish, goldfish, cherry shrimp, or other slow-swimming animal, consider implementing one of these techniques to reduce the current in your aquarium.

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. If you see your fish struggling, don’t be afraid to downsize your filter to better accommodate their needs.

A sponge filter with a small pump, such as the USB nano-air pump, is our favorite type of filter for gentle flow. 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. Some air pumps come with a flow dial to lessen the air pressure if needed, but if the pump isn’t adjustable, you can also add an air valve outside of the fish tank to reduce the amount of bubbling. If you prefer to use another type of filtration like a hang-on-back or canister filter, check to see if it has an adjustable switch or knob that allows you to modify the flow rate of the water entering the aquarium.

Sponges offer gentle flow that won’t harm your fish fry or bettas and other nanofish.

Baffle the Output

You can use many methods to divert, baffle, or block the water flow from the filter to lower the water pressure. 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. Spray bar holes can be directed towards the aquarium’s back wall in order to decrease the current.

Attach a prefilter sponge or spraybar to the filter output in order to reduce the water pressure.

If you have a hang-on-back filter with a waterfall output, there are several filter baffle techniques that can help reduce the flow while still allowing some surface agitation. 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. Many people also recommend using a soap dish container with suction cups and attaching it to the aquarium wall right under the waterfall. To further dampen the flow of water, add some foam, marbles, or moss to the soap dish.

For water resistance, place live plants, hardscapes, and fish tank ornaments under the waterfall or in front the filter output. Adding decorations and plants to the aquarium will cause the water to break down and slow down. 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, plants, or decorations under the waterfall of your hang-on-back filter to lessen the flow.

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