How to Enhance Water Circulation in Aquarium Sponge Filters

Sponge filters are among the most popular types of aquarium filtration systems. They are frequently employed by experienced fishkeepers, wholesalers, and fish farms that breed millions of ornamental fish.

Advantages:

• They are simple to use and easy to clean.
• Their reliability is extremely high due to having very few mechanical components.
• They are gentle enough so as not to suck in any baby fry, dwarf shrimp, or betta fish with long, flowing fins.

However, sometimes the water flow can be a bit too gentle, failing to generate sufficient water circulation within the aquarium. How can we address this issue?

Operating Principle of Sponge Filters

Normally, a sponge filter operates in the following manner:

1. An air pump is positioned outside the aquarium. It propels air through the airline tubing, which is connected to the hollow core inside the sponge filter.
2. As the bubbles ascend within the sponge filter, water rushes in through the sponge material, trapping particles within the sponge walls. (These particles serve as a food source for beneficial bacteria, which help purify the aquarium water of harmful chemicals produced by fish waste.)
3. The bubbles in the middle of the sponge flow out of the uplift tube and burst at the water surface, creating surface agitation.

The Design and Benefits of “Easy Flow” Uplift Tube

For the sponge filters of Aquarium Co – Op, we’ve designed a curved uplift tube named “Easy Flow” to redirect the water current. This enables the bubbles and water to shoot horizontally across the water surface. This simple modification brings several significant benefits, improving the overall filtration performance in our aquariums.

1. Superior Water Circulation

In the freshwater aquarium hobby, water circulation isn’t discussed as much as it is in the saltwater hobby. Nevertheless, it impacts the ecosystem’s health in numerous ways.

• Benefits of good water circulation:
  • A good water current helps evenly distribute oxygen, plant fertilizers, baby brine shrimp, powdered food for baby fry and filter – feeding organisms, and more throughout the aquarium.
  • When you have a fish tank (especially a larger one) filled with rocks, driftwood, and decorations, dead zones may form where the water flow has difficulty reaching. These stagnant areas often accumulate unsightly debris and promote algae growth. By directing the spout of the Easy Flow towards these sluggish areas, the detritus is stirred back into the water column, allowing it to be sucked up by the sponge filter.
• Example of water flow adjustment:
  • For instance, most people place the sponge filter in one of the back corners to keep it out of sight. If there are a lot of plants or other decorations blocking the way, the water current in the front of the tank is much slower, and mulm (the fluffy, brown “dust” on the substrate) tends to accumulate there, where it’s most visible. Instead, aim the Easy Flow uplift tube so that the spout points towards the middle of the front aquarium wall. The water current will flow across the surface, hit the front wall, and then travel downwards, thus pushing the mulm towards the middle and back of the aquarium, making it less noticeable.

2. Enhanced Surface Agitation

Moving water at the top of the aquarium is crucial for the health of your fish.

• The importance of gas exchange:
  • It promotes good gas exchange, where carbon dioxide (a waste product excreted by your fish) is released into the air, and fresh oxygen from the air dissolves into the water. In a previous experiment, we demonstrated that filters that agitate the water surface result in significantly higher dissolved oxygen levels in the tank. With a traditional sponge filter featuring a vertical uplift tube, the bubbles rise and create circular ripples in the area just above the sponge filter.
• Advantages of Easy Flow in surface agitation:
  • However, the spout of the Easy Flow uplift tube can be easily extended to sit right at the waterline, enabling the bubbles and water flow to shoot horizontally across the tank, increasing the amount of surface agitation. This not only prevents the formation of an oily biofilm on the water surface but can also push away floating plants, creating a larger area for gas exchange to occur. If you find that the surface current is too strong for some of your top – dwelling fish, the Aquarium Co – Op air pump has an adjustable air – flow control, or you can install an air valve to reduce the speed.

3. Improved Bubbling

One common complaint that fishkeepers have about sponge filters is the bubbling sound when the bubbles burst at the water surface.

• Noise reduction effect:
  • Some people find the sound soothing, while others don’t want their tank to sound like a cauldron. Our founder, Cory, manages an entire fish room with over 30 tanks, most of which are equipped with sponge filters. The combined effect of so many sponge filters definitely raises the overall noise level in the fish room. Since switching to the Easy Flow uplift tubes, the measured decibel level in the fish room has dropped significantly to approximately 40 dB, which is comparable to the noise level of a quiet library. Instead of agitating the water vigorously in a single, concentrated location, Easy Flow helps distribute the bubbles (and their popping sounds) evenly across the entire tank surface, minimizing the overall noise.
• Reducing moisture – related problems:
  • Besides the decibel level, we’ve also observed another advantage resulting from the different bubble – popping pattern. In a traditional sponge filter, the bubbles all burst in roughly the same area of the tank, causing water to splash up and adhere to the aquarium lid and rim. This excess moisture often leads to the growth of dark – green algae sludge and the formation of white mineral deposits if you have hard water. In contrast, the horizontal surface current of the Easy Flow causes the bubbles to travel further and not always burst in the same spot, thus reducing the amount of moisture on the lid and rim. Take the previous example where the sponge filter is placed in the back corner and the Easy Flow uplift tube is aimed towards the middle of the front wall. Depending on the air pressure of the air pump, most of the bubbles end up bursting somewhere in the middle of the tank, keeping the rims free from crusty mineral deposits. Additionally, the glass lid is somewhat drier than before, reducing the growth rate of the algae sludge.
• Preventing algae growth on the uplift tube:
  • If you have a glass lid and are using an external aquarium light like the Easy Plant LED, we have an additional tip to prevent algae growth on the top of the Easy Flow uplift tube itself. Purchase a plastic, black folder and cut out a square or rectangular piece large enough to shade the top of the Easy Flow. Place the plastic folder piece on the glass lid so that it is beneath the light and covers the Easy Flow. Generally speaking, you won’t have plants growing directly where the sponge filter is located, so a little shade in that corner of the tank won’t negatively affect plant growth.

4. Efficient Flow

Normally, a sponge filter produces large, intermittent bubbles accompanied by a loud, glugging sound.

• The advantage of small bubbles:
  • However, if you can make the bubbles much smaller, it not only reduces the noise level but also makes the filtration more efficient. A steady stream of tiny bubbles generates continuous lift and suction in the sponge filter – similar to how an escalator runs continuously while an elevator starts and stops frequently.
• The design of the air collar:
  • Previously, to create this flow of small bubbles, we recommended using an air stone inside the sponge filter. Over time, however, the airline tubing connecting the air stone to the sponge filter would eventually harden, causing the air stone to slip or completely fall off. Therefore, we designed the Easy Flow uplift tube to come with an air collar at the base. This air collar also diffuses the air from your air pump into smaller bubbles in the water. The air collar completely replaces the air stone while still providing the same benefits of quieter bubbling and optimized filtration. Moreover, it completely prevents any bothersome bubbles from escaping from the sides of the sponge walls.

Conclusion

If you’ve never used a sponge filter with an adjustable, curved uplift tube, you should give the Aquarium Co – Op sponge filter a try. For the older versions of our sponge filter, you can purchase the Easy Flow upgrade kit for small, medium, and large sizes, as well as for nano sizes sold in 2024 or later. If you purchase any of our sponge filters nowadays, they all come with the convenient Easy Flow uplift tube. So give it a shot and instantly enhance your aquarium filtration.