The Internet provides us with a very fast way to share these experiences and hopefully to learn from them. The wide range of equipment available to the average hobbyist is staggering in sheer number and variety. This can be intimidating to beginners and even experienced fish keeper's alike. The intent of this article is to provide enough information to demystify the process and familiarize them with some of the major players without getting into brand bashing.
The main goal of water filtration in an aquarium is to provide a healthy environment for our fish and to extend the time between regular water changes. More on that later… We also filter the water to make the aquarium a lot more pleasant to look at. The lakes and streams most of the fish in our hobby originally come from are rarely ever what any of us would call…sparkling clear.
The fish don't mind this natural situation but not many of us would put up with it. Proper filtration can be the difference between an aquarium that is a stunning showpiece and one that more closely resembles an indoor bog. (Note: this isn't always a bad thing. We have people in the hobby who strive to attain this look.)
OK… now that we know what aquarium filtration IS and what we want it to do for us. We just need to learn how to go about it. Basically all Aquarium filtration falls into three established types…
Mechanical Filtration
This is the simplest form of filtration of all and consists of nothing more than running the water through a porous material in an effort to trap as many of the suspended particles as possible. The smaller the openings are in the chosen material…the smaller the particles that are trapped will be and the cleaner the water. So why don't we just use a fine sheet with microscopic openings? We do…it's called Reverse Osmosis or RO and produces amazing clean water but there's a problem with it.
Flow rates (the speed water moves through filter media) decrease a great deal as the size of the openings get smaller or as it clogs. Pressure systems use a powerful pump to force the water through these smaller openings at the expense of a lot higher electrical draw. (RO systems generally use the already existing water main pressure of 40 to 65 PSI.) These filter systems are very efficient but are measured in terms of gallons per day rather than gallons per hour. Not quite the sort of turn over rate we're looking for.
Turn over rate by the way is the number of times the aquarium water is replaced in a given time period. (Usually an hour) A 50 gallon tank with a 400 gallon per hour HOB filter will have an 8x turn over rate. The efficiency of the filter system itself will determine just how large a turn over rate you actually need. Biological filtration is the main limiting factor in this. BB need a certain amount of contact time with the water in order to work it's magic. We compensate for this by running a higher turn over rate.
The type of fish kept, as well as the stocking level in the aquarium, has an impact on the turn over rate equation. Efficiency levels of the different aquarium filters vary so there is no hard and fast rule to turn over rates but you can use the following information as a guide.
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Wet/dry sump systems … 3X to 4X
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HOB filter systems … 4X to 6X
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Canister filters … 6X to 8X
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All systems on heavily stocked aquariums … 10X +
Chemical Filtration
Removing harmful chemicals from the water is a lot more difficult than solid waste because they are liquid and can't be trapped like suspended particles can. Certain materials however attract these chemicals and contain them. Carbon… Zeolite… ECT. These materials are usually placed in flow-through bags or special baskets and the water is then run through them. Not all of the water comes into contact with the Chemical media on each pass but eventually the levels are lowered to an acceptable amount.
Carbon does a great job of removing odor causing chemicals out of the water and has also been suspected of lowering the trace levels of growth inhibiting hormones in the water. (This is one of nature's ways of controlling population in any given body of water and also has a huge effect on breeding.)
There is a great deal of debate in the hobby about the usefulness and even the wisdom of running chemical filtration at all times. Both sides have compelling evidence and no clear cut winner has emerged in the hotly contested debate. Personally I think that a small amount of chemical media is beneficial but that in most cases it's taken to extremes. Chemical filtration media has a natural saturation point as so needs to be replaced periodically. After this happens the saturated media begins to release the chemicals back into the aquarium
