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. Perpetually fighting against fast flow can cause your fish to get whipped around the tank, start hiding in shelters, and potentially develop illnesses from the constant stress. 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 that has slow flow

The simplest way to reduce the current is to not use too much filtration 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. Don’t be afraid if you notice your fish are struggling to get the filter downsized to meet their needs.

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. 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. 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.

The Output can be baffled

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. If the water bounces off the wall or surface, it loses its kinetic energy and the current falls. 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. Some canister filters let you attach a spraybar to the output to reduce the energy loss as the water is dispersed through a series 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.

There are many filter baffle options that can be used to reduce flow in a hang-on back filter with a waterfall output. A block of sponge can be cut to the size of the waterfall, and stuffed into the opening. You can also attach craft mesh to the waterfall opening with 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.

To help reduce the water pressure, you can place live plants, hardscape or fish tank ornaments either in front of or under the waterfall. 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.

Place a soap dish, plants, or decorations under the waterfall of your hang-on-back filter to lessen the flow.

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