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How much and what type of filtration will I need?

Posted in All About Equipment

- Submitted by Bonzo

This article is by no means an exhaustive review of filtration, but merely hits the high points. There are many right ways to filter a tank, as well as many wrong ways. Hopefully the following information helps steer you away from the wrong ways.

Filtration needs depend on several factors including tank size, its occupants, their adult size, and feeding requirements. For large cichlids such as Oscars, generally the more filtration you can provide, the healthier your fish will be.

First we need to discuss what types of filters and filtration and are available. I will group filters into four basic categories: air pump driven filters, hang on back (HOB) power filters, canister filters, and wet/dry sump filters. Filtration can be classified in three categories: biological, mechanical, and chemical.

Filter Types:

Air Driven Filters

Air pump driven filters include sponge filters, corner filters, and undergravel filters. These filters are inadequate as primary filtration in an oscar tank. Sponge filters can be useful for raising fry as well as keeping an easily transferable filter ready to go. Undergravel filters are completely unsuitable for oscar tanks because the Oscars will likely dig up the filter plates. Also, the filter plates tend to accumulate large amounts of decomposing waste that can’t be cleaned out by vacuuming the gravel.

HOB/Power Filters

HOB power filters are the most economical large capacity filters available for aquariums. Power filters can be used as primary filtration in an oscar tank. When choosing a filter, you want to look for high flow rates, large media capacity, and flexible media configuration. Some power filters require you to use proprietary media, offer limited flexibility, and are engineered poorly. While there are differing opinions, most will agree that Aquaclear and Emperor filters are probably the best power filters available. Both have advantages and disadvantages, but you can’t go wrong with either.

Canister Filters

Canister filters are more expensive than HOB filters, and can run between $75-300 US each. They can provide very high water quality when setup and maintained properly. Canisters generally offer very good media capacity and flexibility, but usually lower flow rates than large power filters. Just as with HOB filters, some canisters are better than others. Some provide very little media flexibility, while others are engineered poorly. You get what you pay for. Most will agree that Eheim, Fluval x05 series, and Filstar XP series are all good filters. Eheim is the Mercedes of canister filters, while Fluval, Filstar, and Marineland are more like Chevy and Ford.

Wet/Dry Trickle Filters

Wet/Dry sump filters can be expensive to setup, but offer the most efficient biological filtration available for freshwater aquariums. That said, they are lacking in mechanical filtration and should be complemented by a canister filter or HOB filters as appropriate for your tank. They also take up more space under your tank than a canister filter. Generally, it isn’t necessary to use a wet/dry, but they are great for large aquariums.

Filtration Types:

Biological Filtration

Biological filtration is the most important type of filtration in any aquarium. Biological filtration involves providing filter media for nitrifying bacteria to colonize. Once the media is colonized, the bacteria break down ammonia and nitrite from fish waste into less harmful nitrates. There are several ways to provide bio media in your filters. These include sintered glass media (Eheim Ehfisubstrat, Seachem Matrix, Cell-Pore), ceramic media (Fluval BioMax, Bio Chem Stars), bio balls, sponges, and bio-wheels.

Mechanical Filtration

Mechanical filtration removes solid waste particles from your tank water and polishes your water to keep it looking clean. Sponges, filter floss and ceramic noodles in varying configurations are the most common type of mechanical filtration. Good mechanical filtration is critical in an oscar tank. They are messy eaters and produce a tremendous amount of waste.

Chemical Filtration

Chemical filtration is mainly an auxiliary filtration type in that is not necessary to maintain a healthy aquarium. Chemicals are available to remove ammonia, nitrite, nitrate, phosphates, heavy metals, and many other water impurities. If you rely on chemical filtration in lieu of biological filtration, you will be susceptible to tank crash if you don’t replace the chemical media before its capacity is used up. The most common type of chemical filtration is activated carbon. Carbon removes odors and harmful chemicals from your water, but its lifespan is very limited. In reality it’s not necessary to use carbon consistently. Its best use is to remove excess medications and chemicals from a tank after treating a disease.

How much filtration do I need?

How much filtration you need depends on the size of your aquarium, its occupants, and to some extent what you’re willing to pay. In general, it is helpful to have 10x your tank volume in filter pump capacity, especially when using HOB filters. Note this doesn’t mean the manufacturer’s stated filter capacity, but the flow rate of the filter pump. It is also wise to have at least two filters to give you redundancy as well as to stagger maintenance intervals.

On the bottom end of the price range, a pair of large HOB filters can handle a tank between 55-75 gallons. If you’re willing to spend more, a single large canister and one large HOB filter can filter a 55-90 gallon tank. As you get into larger tanks, it is wise to use canister filters as your primary filtration. A good minimum for a 125 gallon tank would be a pair of large canister filters. Everybody has their favorite filters and some use more or less filtration than others. If you’re in the market for new tanks and filters, ask questions before buying. It can help your decision making process, save you some money, and possibly some grief. The bottom line is to buy whatever you can afford. If you have to, spend more on filtration and buy decorations later.