Filtration strategies

Considering how many members have questions about brands and types of filtration, there's another side of things; multiple filters.

By that I mean two or more filters on your tank. One can not over filter a aquarium. I am not talking about the media within the filters, just that the more water filtered the better water quality maintained.

I read in an old Tropical Fish Hobbyist Magazine (Oct. '03) about a fellow who had, among other filtration, both a fluidized bed and Hang on Back (HOB) power filter on his 55 gallon reef aquarium. That, along with his protein skimmer, kept his reef in top shape. The person was concerned about the weight on the back of the tank from all that filtration.

The recommendation was to build wood boxes for particularly the fluidized bed filter to sit on.

But I digress. There are many, many benefits from using two or more filters on your tank.


First, your fishes. Though most freshwater fish are adaptable to varied levels of pH, temperature and hardness, marine fishes are not. It is up to the keeper to keep their charges in stable, clean water.

More than one filter can really help accomplish that. For example, there are two canister filters, both rated for up to a hundred-gallon aquarium, filtering the 75 gallon freshwater tank to my right as I write this. There are roughly 55 tetras and multiple other small fishes in it. Those fishes are nearing their 14th year.

Without getting too technical on the hows and whys, it's because of top shelf water quality from multiple filtration.

The only caveat is the flow from too powerful multiple filters that makes it difficult for fishes to swim. So when you buy filters, make sure they are rated for no more than twice your tank size. Fishes like Bettas need considerably less flow.


Cleaning. What makes aquarium keeping possible is Nitrifying bacteria. When a person has one filter, those bacteria are impinged by the cleaning, even when the filter is cleaned in tank water as it certainly should be.

That can result in a mini Ammonia bloom until the bacteria fully rebound, which can take days. And readers of this should know that Ammonia, even a tiny bit of it, can damage fishes, particularly the lining of the gils. If one visits the forum daily, you'll see many unexplained deaths. Now you know why.

With multiple filters that can be negated. Say you have two HOB power filters for example, and you clean filters monthly. You can clean one HOB one month, the other HOB the next month. As long as your tank isn't grossly overstocked, that is.

Stability is the name of the game of aquarium keeping. Multiple filters can help.


Media. The more filters you have attached to a tank the more media you can use. Too much Phosphate causing algae? Add removal product to the filters, problem solved.

There is filter media available for nearly anything that is dissolved in water. Though canister filters, by their very construction, can hold more types and amounts of media than a HOB filter, more than one of any kind of filter is a very good thing.

Clean water is what every forum member should aspire to.


And there is water volume. In nature, marine and freshwater fishes have a great deal more water to swim in than any aquarium does.

Thus, the more water in a system the better. Multiple filters can provide it.

HOB power filters that are waterfall type, hold little water volume, but any extra is good. Canister filters hold more; many brands hold over a gallon of water.

Though refugiums are a marine thing, they also work in FW. It's beyond the scope of this post to describe details of FW refugiums, but hang-on models hold a good deal of water, from one to five gallons, depending on size and model.

If one has sump-based filtration, filters can be attached to it, keeping them out of sight. I'm one who detests the appearance of equipment in an aquarium, so all my tanks have sumps.

Water volume is another plus when using multiple filters.


So, to summarize. Using two or more filters on an aquarium can benefit your fishes. And benefiting the fishes is always a good thing.