Reviewed: 3 Best Selling Internal Aquarium Filters for Tanks 30 Gallons or Smaller

Bottom Line:

⇒ 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):

Tetra Internal power filter

Aqueon Quiet Flow 20

Penn Plax Cascade 400

In this article: I purchased and tested three different internal aquarium filters. 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:

Author Bio: Don Glasgow - creator of this site

* I've been keeping fish for 24 years, including Discus, Angelfish, Betta Fish, Tiger Barbs, Bristlenose Plecos, Zebra Danios and many, many more.

* I've have been keeping planted aquariums for 23 of those 24 years. Plants I've kept include Java Fern, Sword Plants, Rosette Sword and more.

a picture of me

Internal filter designs

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

Image above: Penn Plax 400 internal filter. To see the current price tap here or the picture.

The Penn Plax Cascade 400 has a slim, upright design that makes it easier to hide in an aquarium. It measures 9.5 inches tall, 2.5 inches wide, and 2.5 inches deep. The body is blue, with a black motor at the top.

The company claims the filter can move 110 gallons (416 liters) of water per hour.

The filter attaches to the aquarium glass with small suction cups. This concerns me because rubber suction cups deteriorate over time. Eventually, they may no longer hold the filter in place.

The Three Filter Chambers

The Cascade 400 has three chambers that hold filter material.

The bottom chamber contains a foam block that removes larger debris but allows fine particles through.

The middle chamber is empty. When testing the filter, I added filter floss to this space, which helped remove fine particles from the water.

The top chamber contains a removable plastic container filled with carbon chips. You can replace the media, but the lid was difficult to remove. I had to pry it off with a table knife.

Motor and Water Flow

The motor is fully submersible and located at the top of the filter.

When I first tested the unit, the motor was noisy because its cover was loose. Once I snapped the cover into place, the motor was silent.

Water can return to the aquarium through an adjustable spout that provides aeration or a multi-hole spray bar positioned above or below the water.

Positives and Negatives of the Penn Plax Cascade 400

Positives

The large, empty middle chamber allows additional filter media. I would add filter floss.
You can choose between regular water flow, aerated flow, or a spray bar.
I like the slim, blue design. It makes the filter easier to hide in an aquarium.

Negatives

The carbon media container lid is difficult to remove.
The plastic latches look like they could break easily. I’m not saying they will, but they don’t appear very sturdy.
A hole at the bottom allows water to bypass the foam pad, reducing its effectiveness as filter media.
The small suction cups may become a problem as the rubber deteriorates.

How To Grow Beautiful Aquarium Plants Without Substrate

Aqueon Quiet Flow 20 Internal Aquarium Filter

Buy this internal filter for your tank. Tap Here To View Selection

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 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.

Tetra Internal Aquarium Filter

You can buy this filter by tapping here or the image.

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 inside the aquarium and 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

* 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):

Tetra Internal power filter

Aqueon Quiet Flow 20

Penn Plax Cascade 400

Video: Internal Filter Review

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).

Other pages on this site:

⇒ Freshwater fish species

⇒ How to care for Chinese Algae Eaters

⇒ Internal Filter Reviews