V. Filters - Basic Filtration Choices   

This article discusses Biological Filters, Canister Filters, Protein Skimmers & Media Reactors

   

     In many ways, a reef tank is a life support system for a small piece of the ocean. The abundance of life has the side effect of an abundance of waste, left unmanaged and this waste leads to noxious and outright toxic compounds to the life in our aquariums. Naturally, entire food chains exist dependent on the waste created from life. We can emulate this methodology to manage the waste in our tanks in between water changes to assure the health and growth of all inhabitants.

 

Biological Filters

 

     Referred to as biological filtration, media is populated with beneficial bacteria. Tank water is filtered through this media allowing the bacteria to feed on various compounds contained in the waste, eliminating them entirely or converting them to safer compounds. Regardless of application or target compound all biological filters function on the above principals. The two primary types of biological filters used are "Wet/Dry" systems and canister filters.

 

     Wet/Dry filters are a classic form of biological filtration used by hobbyist and scientific research facilities alike. Tank water is drained from the display and either goes directly into a wet/dry filter or is diverted to one from a centralized manifold or sump. The water is either allowed to pour through a matrix of holes, forcing a consistent trickle or is dispersed using a jet system to spray the water into the filter. The filter itself is usually a box or tube filled with a composite media referred to as bio-media. In addition to the chamber for bio-media, a means of mechanically removing detritus via floss or a filter pad is often designed into most wet/dry filters, if yours does not have this feature a prefilter should be used to prevent build-up of detritus on the bio-media.

 

     Chemical filtration is often less efficiently addressed with many wet/dry systems. Filtration treatments like granulated carbon are often applied by allowing passive exposure to the carbon, water is not usually forced through the carbon. The ability to force water through a specific series of levels with equal exposure to media is where a canister filter really shines.

 

Canister Filters

 

     Canister filters apply the same principle of beneficial bacteria but with the added benefit of a convenient tower-like configuration that assures all water passes through mechanical, biological and chemical levels of filtration. The convenient often "all-in-one" approach, smaller footprint compared to sumps and built-in circulation pump or water return make canisters ideal for a smaller tank that are not frilled or plumbed to accept a sump. Maintenance of a canister filter is usually a matter of monthly exchange of prepackaged media sold by the filter manufacturer and readily available. It is my opinion that with proper consideration and maintenance a canister filter is an adequate filtration option for stand-alone applications on reef tanks up to thirty gallons.

 

Protein Skimmers

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     In situations of larger tanks or higher bioloads, the filtration provided by a wet/dry or canister filter alone is no longer adequate for the amount of dissolved organic waste accumulating in the system. In these situations, a foam fractionation reactor, or a Protein Skimmer should be mounted to the tank or situated in the sump of your wet/dry filter. A protein skimmer mixes water with air in a reaction chamber creating foam. Organic compounds bind to the oxygen and are carried on the bubbles to a collection cup. As the bubble rise, they are concentrated, condensing the compounds into a sludge on the surface of the foam. The foam is eventually carried to the collection cup, the collection cup is routinely removed, cleaned and replaced.

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     Even on smaller systems, protein skimmers serve the same benefit as on larger systems, capturing dissolved organic compounds in the water column and exporting them from the tank. This reduces the build-up of both nitrate and phosphate over time. As many biological filters operate in a manner that creates nitrate as a byproduct,  a protein skimmer may help to reduce nitrate build ups between water changes. However, you may find that even with your biological filtration and protein skimmer reducing nitrogen-based compounds, you are still generating a high amount of phosphate leading to algae growth.

 

Media Reactors

 

    Whether it is due to a heavy bioload, heavy feeding or high phosphate in your source tap water not addressed by adequate reverse osmosis treatment, many reef enthusiast will also employ a biological media reactor that is more purpose suited in addition to the common biological filter and protein skimmer. Most commonly these media reactors will be employed with phosphate in mind and are aptly called phosphate reactors.

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     Phosphate reactors usually consist of a small chamber. This chamber is partially filled with a plant base polycarbonate media. a small pump feeds water into the chamber gently tumbling the media. Bacteria populate the media and begin to digest the media utilizing phosphate in the water as part of the metabolic process. the waste with the now bound phosphate is then left in a thin layer of mucus on the media. The gentle but constant tumbling of the media assures that this layer is consistently knocked off and carried out of the chamber. The chamber of a phosphate reactor should thusly be expelled into a filtration chamber that allows for mechanical removal of detritus so that this waste may be filtered, or into the feed of the protein skimmer so that it may remove the organic compounds created by the bacteria within the phosphate reactor.

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     Filters and filter options as a whole will change in time and it seems like every few years a new innovative filter is designed or media is introduced and we owe it to the nature of exploration to try new approaches and evolve with the innovations of the hobby. However, be mindful of any product that guarantees a total solution to reef keeping. Such systems often come with a level of micro-management or false expectation that will lead to frustration, instead focus on researching your specific challenges and trying to to add additional filtration or turn to chemical intervention only when the practice of routine water changes proves no longer sufficient to maintain low nutrient levels like Nitrate and Phosphate in your aquarium.