Reviewed: 3 Best Selling Internal Aquarium Filters for Tanks 30 Gallons or Smaller
I purchased and tested three different internal aquarium filters to review. The Penn Plax Cascade 400, the Tetra Power filter 10 to 30 gallons, and the Aqueon Quiet Flow 20 Internal Power Filter.
I looked online at internal aquarium filters and then chose the very best, as shown by the number of reviews and the total rating. I also stayed with filters that have common brand names. Here are the results:
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Penn Plax Cascade 400
Current Amazon price……………… $33.43
Number of Amazon ratings……….. 839
Number of stars out of 5……………. 4.0
Aqueon Quiet Flow 20
Current Amazon price……………… $24.95
Number of Amazon ratings…………816
Number of stars out of 5……………. 4.2
Tetra Internal Filter
Current Amazon price……………… $21.95
Number of Amazon ratings…………20,992
Number of stars out of 5……………. 4.2
Question: “What are internal aquarium filters?”
Answer: An internal filter is an aquarium filter in which the motor and most or all of the body of the filter unit sits in the aquarium water. This differs from other filters in which the motor and the body of the filter sit outside of the aquarium.
When I first purchased the three filters, my thought was to compare how well they filtered, so I set up a 20-gallon tank, mixed in some very dusty sand and tested two of the filters one at a time.
These two of the filters took nearly the same time to remove the cloudiness from the water. I didn’t test the third.
The only actual difference was in how they were designed, so that is what this article will cover.
Penn Plax Cascade 400 Internal Aquarium Filter
Photo links to Penn Plax Official company website and opens in a new tab:
The first internal aquarium filter I will discuss is the Cascade 400. It has a slim vertical design, which would allow it to be more easily hidden in an aquarium. The size of the filter is 9.5 inches tall, 2.5 inches wide and 2.5 inches deep.The body of the unit is blue, which would also allow it to be easier to hide. The motor portion is black.
The company claims that this filter unit will filter 110 gallons (416 liters) per hour
It attaches to the side of the aquarium with suction cups attached to the motor portion of the filter. The suction cups are rather small. This is a negative because rubber suction cups degrade in the aquarium over time. This degradation will allow the unit to eventually come loose and lose the ability to be reattached.
The filter has three chambers inside. The chamber at the bottom of the unit, where the water is drawn in has a foam block which would filter out large debris, but not fine matter.
The second chamber is empty. When I was testing the Cascade 400, I added filter floss to the empty area. This allowed the fine particles to be removed from the water column when I was testing it in water.
The third chamber at the top is a plastic container filled with carbon chips. You can replace the media in this container. I will say the lid was very difficult to remove. I had to use a table knife to get it off.
The motor is at the top of this filter unit and is fully immersible. The motor cover came to me loose, so until I figured out what was going on, the motor made a lot of noise. I snapped the cover back into place and then the motor was silent.
The filter can push the water back into the aquarium in two ways: 1. With either a water flow spout that allows aeration to be added or 2. the water can be sprayed back into the tank through a multi-hole spray bar positioned above or below the water.
Positives and Negatives of the Penn Plax Cascade 400
Positives of the Cascade 400
* I like that the empty chamber is large, which allows additional media to be added. I would add filter floss.
* I like that there is a choice of how the water is returned to the aquarium, regular flow, aerated flow, or sprayer bar in or out of the water.
* I also liked the slim, upright blue design. Nice shape and color for hiding it in the tank.
Negatives of the Cascade 400
* The cover to the media container has to be pried off.
* The design of the latches that lock all the parts together seems like they could easily break. Not saying they would, they just look like they could.
* There is a hole that is positioned at the bottom of the unit that allows water to bypass the filter pad. This limits the pads effectiveness for bacterial growth.
* The suction cups are small. Long term, this may end up being a problem because rubber degrades in water.
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Aqueon Quiet Flow 20 Internal Aquarium Filter
The Aqueon Internal Aquarium Filter is a black rectangle shaped box. The one I bought was 7 inches high, 5 inches wide, and 2 inches deep.
The box says that the unit will filter up to 130 gallons (492 liters) per hour.
It came with two filters held in place by a plastic holder: the first filter was a very porous plastic foam filter and a pre-manufactured square floss filter filled with carbon media. The filter floss is disposable and would have to be replaced by buying new ones. The replaceable filter cartridges could be purchased on Amazon at 6 filters for $16 ($2.50 each). Based on past experience, I suspect the filter cartridge would need to be replaced every 4 to 8 weeks.
It is possible to just use filter floss packed down into the filter holder. Doing this would allow the filter floss to be rinsed and reused with the beneficial bacteria still in place.
Water is pulled into the filter through the bottom of the unit and then pushed to the back, where it has to pass through the filters before it can return to the aquarium.
The unit can be placed in the aquarium by four large suction cups on the back or it can be hung on the side using the clips included.
Positives and Negatives of the Aqueon Quiet Flow 20
Positives
* It’s possible to replace the manufactured filter with filter floss, saving money over the years
* It has four large suction cups on the back, which should easily hold it in place
* The water brought into the unit must pass through the filter media before it can return to the aquarium.
Negatives
* It has a fairly large profile for a filter that is to be placed in a small aquarium
* Once the filters were in place, the lid wouldn’t stay on.
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Tetra Internal Aquarium Filter
Photo links to the official company website and opens in a new window:
This black internal filter is 9.75 inches high, 3 inches wide, and 2.5 inches deep.
The internal filters are: 1. a black, very porous filter and 2. a white filter made of filter floss and filled with carbon.
They manufactured this filter unit to hang on the side of the aquarium.
The motor pulls in water at the bottom and it is pushed through the filters and then out via the waterfall lip.
The filter unit has enough room to allow additional filter floss to be added.
The motor has to be unscrewed to be removed. I’ve never seen a design like this. I wouldn’t use this in a saltwater aquarium for fear the screws would rust.
Positives and Negatives of the Tetra Internal Aquarium Filter
Positives
* Very inexpensive – I paid $13.59
* You can add filter floss to the filter media, increasing the filtering capability of the unit.
* The filter can be moved lower or higher in the aquarium by using the hang on clip.
Negatives
* The motor has to be unscrewed (two screws) in order to clean it.
Based on all the information, I would rate the filters as follows:
⇒ Best choice: Tetra Internal aquarium filter
Runner-up #1: Aqueon Quiet Flow 20
Runner-up #2: Penn Plax Cascade 400
All of these filters are great filters and would do what they are supposed to do. The only reason I picked the Tetra Filter is because of the price. You could buy two tetra filters for the price of one of the other filters.
* If cost did not influence my choice, I would pick the Penn Plax 400 because of the large space available for adding additional filter floss or other media.
Again, these are all great filters. Any of the three that you choose will be a good choice.
Amazon Price Check Links (open in new tabs):
Question: “Where should I place my internal aquarium filter?”
Answer: If it were me, I would place the filter at the back of the tank and hide it with the aquarium decor (stones, driftwood or plants).
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