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, flowing fins or are small and not designed to handle large amounts of water. Your fish could become stressed from constantly fighting against rapid flow and get whipped around your tank. If you own a betta, goldfish or cherry shrimp, these are some of the techniques that can be used to reduce current in your aquarium.

Use a filter that has slow flow

You can reduce current by not using too much filter in your aquarium. In their quest to have the cleanest tank possible, people sometimes install multiple filters or get oversized filters that are meant for much bigger fish tanks. Sometimes, hobbyists purchase an all-in-1 kit that is too powerful for their bettas or other slow fish. If you see your fish struggling, don’t be afraid to downsize your filter to better accommodate 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. Its coarse foam is perfect for straining debris from the water without sucking up any baby fish, and the bubbles create good surface agitation to ensure 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 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 offer gentle flow that won’t harm your fish fry or bettas and other nanofish.

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. If the water bounces off the wall or surface, it loses its kinetic energy and the current falls. A prefilter sponge can be placed 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. 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. Spray bar holes can be directed towards the aquarium’s back wall in order to decrease the current.

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

You can use filter baffles to help reduce flow and allow surface agitation with your hang-on-back filter. You can cut out a block of sponge that fits the width of the waterfall and stuff it into the waterfall opening. Attach craft mesh to the waterfall opening by using string or zip ties. Many people also recommend using a soap dish container with suction cups and attaching it to the aquarium wall right 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 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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