The Best Of The Best Internal Aquarium Filters Currently On The Market 2023

I recently purchased three different internal power 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 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:

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 Filter

Photo links to Penn Plax Official company website and opens in a new tab:

The first internal power 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

Aqueon Quiet Flow 20 Internal Power Filter

Photo links to Aqueon official company Website and opens in a new tab:

The Aqueon Internal 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

Tetra Internal Power 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 Power Filter

Based on all the information, I would rate the filters as follows:

Best choice: Tetra Internal power 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.