Filter Fundamentals

There is a variety of aquarium filters on the market, and choosing the right one may not be as easy as you think.


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Over the years, filters for fish tanks have changed a great deal. I can say—without reservation—today’s modern filters are vastly different from the ones that preceded them, but with a number of limitations. Let’s face it, not everyone out there is capable of selecting the proper filter media.

 

Somewhere along the line, many companies got the bright idea to design filters that would only work with filter cartridges that fit their various models. This creation of proprietary filter cartridges was a boon to both the retailer and the manufacturer, but not so much the consumer. Today, there are few hanging filters that do not require specific cartridges if you want them to perform to maximum efficiency. Needless to say, a customer would always prefer a choice, if given one.

 

The best external hanging filters of the past were not designed like the ones of today. There was a motor on top that sucked aquarium water up one, two or even three lift tubes. It was delivered directly onto a plastic plate covered by whatever you wished. Usually, you would buy a roll of non-glass insulation and from that cut a pad that would fit perfectly on the plate. On top of the pad, you could put a layer of charcoal and cover it with filter wool. The water from the tank passed through these elements and was returned to the tank through the plastic housing under the motor. The stream of returning water came out of a simple tube, which you could direct in any direction you wished. If you wanted the returning water to move to the far end of the aquarium from where it was pulled, you simply used an extension tube.

 

Today’s external or hanging filters return the water with a waterfall or cascade effect. This diminishes as the filter cartridges become clogged. While the waterfall offers the added benefit of some oxygenation to the water, the water returns straight down almost to the point where water is sucked into the filter, resulting in the same water getting sucked up again. If you are getting the impression that I like the old filters better, you are right. The motor stuck up above the tank, so the look was not appealing, but boy did it work.

 

History Lesson

Another filter option is a canister filter. I was around for the first ones in the hobby. Out of Europe came a model produced by a company who also made a fish food. The one I had worked fairly well until the motor burned up one night and almost started a fire. The impeller bound up due to plant matter.

 

Then, from the U.S. came a modular filter called, aptly, the MOD-4. It was a series of separate disc-shaped modules made from an unbreakable polycarbonate called Lexan. It worked well, with an external motor that pulled the water through the modules. They were clear, so you could see if they were becoming clogged. As it turned out, this was the prototype for the modern canister filter with separate modules all stacked inside a single canister.

 

I like canister filters, sort of. What I don’t like is the fact that water is sucked all the way down long hoses to a canister hidden from view. It is then returned back up to the top of the aquarium. The use of separate siphon and return hoses makes it easier to keep the intake and output far apart, which is great for water circulation. The problem is you can’t see what is going on inside the filter. To some extent, a reduction of water flow indicates the media needs to be changed, but it can also mean there is a problem with the impeller. I have opened up canister filters to find live juvenile fish, gravel, plant matter, fragments of filter material and, of course, bits and pieces of dead fish. Every type of filter has its drawbacks.

 

Some modern canister filters have evolved to be smart. If consumers want to spend the money, they can buy filters that connect to a computer, which will indicate what is going on in the filter and the tank. Unfortunately, the cost for this level of sophistication is rather dear. Few people will be willing to pay the price, except for those already addicted to programmable LED lights and wave-making power-heads. Don’t hang your hopes on selling large quantities of these modern wonders.

 

In my opinion, the very best filter ever designed for fish tanks that are 30 gallons or smaller was the box filter. Does anyone remember these? You sit them in the corner of a tank, or two corners if it’s a larger aquarium. Then, connect the filters together with a gang valve and use airline tubing to tie everything to an air pump. This kills two birds with one stone—you get both filtration and aeration. In the box filter, you can use any media you wish, but typically, you would employ charcoal and filter wool.

 

The Nitty-Gritty

When I started in the aquarium hobby in 1965, I found that using glass wool in filters was the cheapest route to go. The problem was that if you didn’t use gloves to handle the wool, those glass fibers could stick right into you. Of course, this glass wool was meant for insulation; I merely adapted it for my own use. Soon enough, companies were selling bags and boxes of filter wool. The other option was charcoal, which back then was made of animal bone from slaughterhouses that was converted to pure carbon.

 

Now, we have super activated carbon that has been modified originally from carbon used in the dry-cleaning industry to remove toxic chemicals from clothes after the dry-cleaning process. Back in the day, you had to be certain that bulk activated carbon had not been manufactured for use in the dry-cleaning industry because that carbon would not work properly underwater.

 

Another option was peat for acid-water aquariums. You could get it at home and garden centers, but you had to be careful. Typically, toxic chemicals were added to kill off unwanted invasive weeds. You needed 100 percent organic peat with no additives. I resorted to peat pellets, which worked quite well.

 

What about motors? The motors on the old hanging filters were big and powerful. They returned the water with great force, but it was always under the water’s surface, so there was no noise. Over-flow filters produce a good deal of noise as the water pours back into the tank. Personally, the sound of flowing water has always been soothing to me, but some people would prefer something less invasive.

 

Finally, let’s talk about the intake tubes on filters. On the old-style models, all you needed was a slotted endcap that prevented fish from being sucked up. Bits of debris, plant or otherwise, would be sucked up and deposited on the filter plate and have no opportunity to reach the motor impeller. Today, the covers to the uptake tubes are severely slotted so only water enters the tube. If debris enters, it will go straight to the impeller. This can cause it to jam and/or stop. That’s not possible with the old filters. Now, I am pulling plant debris off the intakes of the overflow filters almost every day.

 

Indeed, the thrills of yesteryear are gone but not forgotten. And speaking of that, this column marks my 25th anniversary of writing the aquatics column for Pet Business. It’s been an interesting experience to watch the evolution of the hobby and the industry. To be certain, not everything is positive—but we must play our hands with the cards we are dealt. I hope the future turns out to be brighter than the past. In conclusion, I offer these pearls of wisdom. The more things change, the more they eventually cycle back to conservative principles that will always be dependable rather than flashy. Don’t put a filtration product on your shelves until you try it yourself. Not every new idea is a winner—you have to be the judge. PB

 

Edward C. Taylor has been in the pet industry for more than 40 years as a retailer, live fish importer and wholesaler, and fish-hatchery manager.

 

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