I’ve had my Fluval FX4 running on my 125-gallon aquarium since about 2020 housing a large male Jaguar Cichlid, named Peep. I have only cleaned this filter one time, and I couldn’t even tell you when that happened because it’s been years. Even so, the filter has never had a single issue and the water remains clear with no smell.
In this review, I will tell you why the FX4 is a must-have for your larger aquarium.
What I think of The Fluval FX4
It’s probably my favorite canister filter I’ve ever owned.
The FX4 is Fluval’s second-largest aquarium canister filter behind the FX6. More powerful than the Fluval 407, the FX4 is great for large aquariums in the 90-180 gallon (340-681 liter) range. Let’s take a look at the specs.
Specs:
FX4 Pros:
1. They’re Silent
A common complaint with aquarium filters tends to be that they’re noisy. The fx4 is as quiet as a mouse, I have to put my ear up to the filter to be able to hear any kind of sound. Mind you, that’s after years of it running too. I’ve had no issues with vibrating, clicking, grinding, nothing. So if you’re concerned about noise, this is the perfect filter for you. In comparison, the 407 and the 207 both lasted years (and are still running) but I do have more noise with that line of Fluval filters. Specifically, clicking and grinding.
About once every 12 hours the filter will shut off and reprime itself, and that might make a noise, but it is short-lived.
2. Media Capacity
I love the multiple baskets this filter has. You can fit a ton of your preferred media into the baskets. As you can see, I mostly have my custom media in mine. I tend to rely on polyester fiber mostly, along with sponge and bio media. I’ve never been a big fan of chemical filtration like activated carbon other than when I need to remove color, smell, or meds.
I mixed Seachem Matrix from the old filter with the ceramic media the FX4 came with when I upgraded. This way, the new tank was instantly cycled matching the bioload from Peep’s old tank.
3. Two-way Outlet
The outlet comes with two adjustable heads so that you can have water flow out of the filter in totally different directions. Of course, you can always use customized pieces like a sprayer bar. I don’t need anything special and I like the outlets it comes with.
4. Filtration Quality
The FX4 is extremely efficient at polishing your water if you have the appropriate media in the filter. The media it comes with is highly effective, but adding polyester fiber makes this filter beyond excellent with water clarity. So if you go with the media it comes with, it will still make your water extremely clear. However, polyester can supercharge this filter even more.
FX4 Cons:
To be completely honest with you, I have not encountered very many negative things about this filter. So I will try my best in this section to be a little objective.
1. A Bit Expensive
When this article was written, the FX4 was running for about $310 on Amazon and about $330 on the Petco website. This is not cheap, however, I think it’s completely worth paying if you have an aquarium above 90 gallons. You aren’t gonna find a high-quality filter that will fit a tank of this volume for less unless you’re skilled enough to make your sump filter.
I would also highly suggest never buying one of those knockoffs you find on eBay.
2. It’s Pretty Heavy
This filter is pretty heavy, and if you’re not very strong, you’re handicapped, or injured, it might be a good fit for you. Or you may need some help with cleaning them. If you’re like me and have a bad habit of not cleaning your canister filters for long periods, this might not be much of an issue.
My Final Thoughts On the Fluval FX4
The pros outweigh the cons of this canister filter. If you have an aquarium between 90 gallons and 180 gallons, this is the filter you should go with, without a doubt. It might be a bit of an investment, but the value it brings is worth the price. It’s quiet, has a lot of room for the filter and media of your choice, has a two-way outlet system, and will leave your tank pristine.
