Aquarium Filtration and Heating
Aquarium filtration
Types of filters
Heaters
What Does Aquarium Filtration Do?
Many people ask the question, “Do I really need a filter in my tank?” The answer is usually “No…but…” So what does a filter actually do, and why is it best to have a filter in a tank?
A filter performs a variety of functions which can be divided into four main groups;
Mechanical Filtration
The main function of filters, one that many people think of, is the removal of dirt and debris from the water, trapping it in the filter media (such as the sponge or filter wool). This debris can include uneaten food, fish wastes, or any other inert particles suspended in the water. This is termed mechanical filtration – that is, it mechanically removes solid matter from the water.
This particulate matter still needs to be removed from the aquarium system by rinsing the sponge or changing the filter wool periodically. The amount of time before the filter media becomes clogged will depend on the type and density of the filter media being used. Generally, it is recommended that the filter media be cleaned every 2-4 weeks.
Biological Filtration
The second important function of filtration is biological. Fish produce waste products, the main one being ammonia. Ammonia is very toxic to fish and so needs to be broken down into less toxic forms. This is done by bacteria (don’t worry – this is good bacteria that you want to preserve). The bacteria Nitrosomonas sp. utilises the ammonia excreted by the fish and converts it to nitrite. Nitrite is still harmful to fish, so a second group of bacteria, the Nitrobacter sp. then converts this nitrite to nitrate. This is what biological filtration entails – the conversion of fish wastes into less toxic forms by the action of bacteria.
The bacteria that performs this task colonises on every surface of the aquarium including the gravel, plants and glass. However the majority of the population works in the filter media. This is where the greatest flow of water occurs, and so this is where most of the biological filtration will take place. Because it is very important to preserve this bacterial population in the filter, never wash filter media under the tap where chlorine can kill it.
Chemical Filtration
This is an often forgotten aspect of filtration, and not all filters will perform this action. Chemical filtration occurs where water is passed through a substance and is chemically changed in some way.
The media used in chemical filtration needs to be placed inside the filter. Some filters will provide cartridges or inserts for chemical filtration, whilst others will not. The types of filter media that perform chemical filtration include:
Activated Carbon – Absorbs many organic substances from the water including colour and odour producing substances. It also removes medications and heavy metals such as copper from the water. It doesn’t remove ammonia, nitrite or nitrate from the water. In a home aquarium its main purpose is the help improve water clarity. Note that the cheaper carbon is not as good in quality as activated carbon and will need changing more often – every 2-3 weeks. Activated carbon will need changing every 3-6 months.
Ammonia Remover or Zeolite – These remove ammonia from the water. Some filters have ammonia remover inserts, or you can get filtration media that will remove ammonia from the water
Coral Gravel and Shell Grit – This media is usually used to help raise the pH of water. It’s main use is in aquariums where the water has a tendency to turn acidic and has difficulty in staying neutral, or with fish that need a higher pH.
Peat Moss – This is used to soften water, and is often used for discus aquariums which need soft water. Peat moss may also induce spawning in many fish. It will turn the water a slight brown colour.
Oxygenation of the water
The fourth function of filtration is oxygenation of the water. Filters perform this by the constant circulation of water in the tank. This brings new water to the surface, thus allowing diffusion of oxygen down through the water surface. It is important to stress that visible air bubbles in the aquarium provide very little oxygen. Oxygen only diffuses from the air down through the water surface. The function of bubbles, either from an air pump or as an attachment of a power filter, is to increase the turbulence of the water surface, thus increasing the surface area for diffusion to take place.
So...do tanks need filtration?
If you have a aquarium smaller than 18” (45 cm), you do not need a filter however your fish will be much happier with a filter. If you do not have a filter the main problem is the build up of fish waste and the decreased oxygen diffusion rate. This can be counteracted by changing about 10% of the water daily and not over stocking the aquarium. It is also advisable to decrease the number of fish that would normally be kept in the aquarium. If you are going to keep fish without a filter, make sure you check out our ‘Small Bowl’ information sheet.
As the water temperature increases, such as during summer, the capacity for water to carry oxygen diminishes. This means that the warmer the water temperature, the less oxygen is present in the water. For this reason a filter, or at least an air pump with an air stone, is advisable.
However, if you purchase a filter, not only will the fish be happier due to the improved water quality, but there is less maintenance involved. Depending on the size of the aquarium, a 1/3 water change will be needed only once every week or two.
Types of Filters
There are many different types of filters available on the market today. However, even though the numbers of different brands can sometimes be confusing, these filters all fit into 6 general categories;
An air pump will be needed for all air driven filters and undergravel filters.
When using a power filter, the aim is to turn the water over in the aquarium about 4-5 times an hour for most freshwater fish. For example, a 100 litre aquarium will need a filter that pumps about 400-500 litres per hour. You could also use two 200-250 litre per hour pumps to achieve the 400-500 litres per hour result.
Air Pumps
All air driven filters will need an air pump to drive them. Air pumps vary in size, and the size needed will depend on the size of the filter and depth of the tank. Generally, a single outlet air pump can be used up to about a 24” (60 cm) or 30” (76 cm) aquarium.
We stock several brands of air pumps. The Eterna and Aqua One air pumps are good basic air pumps with a full range of spare parts available. The Eheim air pumps are of a much better quality and are the quietest air pump on the market today.
The placement of the air pump in relation to the aquarium is very important. If the air pump is below the level of the water (ie. underneath the aquarium), there is a chance that water will backflow from the aquarium into the air pump when the power is turned off. For this reason, it is always recommended that you purchase a Check Valve. This is a one-way valve that is placed in the airline hose. It allows air to go to the aquarium, but prevents water from reaching the air pump.
Air Driven Filters (excluding Undergravel filters)
All of these filters will need an air pump attached to them in order for them to work. There is a variety of air driven filters on the market. Simple corner filters, with the filter wool and filter carbon are the most common, however these filters are becoming old-fashioned as newer types become available. These corner filters are set up with a thin layer of filter wool, followed by a thin layer of carbon, and then finished with another layer of filter wool. The filter wool in the top layer should be changed every 2-4 weeks. The carbon and filter wool in the bottom layer should be changed every 4-6 weeks. Never change both filter wool layers at the same time, as bacteria populations need to be preserved.
Another popular filter is the Hagen Mini Sponge Filter. This filter is small and compact and has a removable sponge and carbon pad. The sponge will need cleaning every 2-4 weeks, and the carbon pad will need replacing every 3 months. The sponge will only need replacing when it starts to loose its shape. Sponge and carbon refills are available. These filters also come with some airline hose.
External sponge filters, with the sponge on the ‘outside’ of the filter are especially good for baby fish, as food is trapped on the sponge and fry can pick on it. Kis Bio-Max and the cylindrical sponge filters are examples of this type of filter. They are not good for larger fish as they tend to chew at the sponge, meaning that the sponge will need to be replaced more often.
Undergravel Filters
Undergravel filters can be attached either to an air pump or to powerheads. Air pumps are fine up to about a 36” (90 cm) aquarium, however for aquariums larger than 36” consider using powerheads. It should noted that undergravel filters, whilst being an excellent filter, are becoming less popular in favour of internal and external power filters.
Undergravel filters consist of a filter plate and uplift tubes. The filter plate sits underneath the gravel, covering the bottom of the aquarium. At least 66% of the aquarium bottom should be covered to make this filter effective, although the more covered the better the filtration will be. Cover the filter plates with a layer of gravel at least 5 cm thick. Finer gravel works best (3 mm or 5 mm). Finally, connect the uplift tubes to either the air pump or powerheads.
These filters work by pulling the water down through the gravel. The gravel acts as the filter, trapping all the debris and dirt. Water then travels underneath the filter plates and up the uplift tube with either the bubbles or via the powerhead. This creates the current necessary to move the water around. The one disadvantage of this filter is that as the gravel is acting as the filter media, the gravel will get very dirty, and for this reason a gravel cleaner is necessary and should be used at least once every 4 weeks.
Another disadvantage of an undergravel filter when attached to an air pump is the noise. Not only will there be the noise of the air pump itself, but also the noise of the bubbles breaking at the water surface
The advantage of undergravel filters over other types of filters is the amount of biological filtration that is done. Because the whole volume of gravel is acting as the filter, a very large and healthy population of bacteria builds up to help break down the fish waste. Undergravel filters also provide a very even filtration as they cover the whole of the bottom of the tank.
The undergravel filters that we stock are the Hagen Clearflow range. These undergravel filters are very good quality, and spare uplift tubes are very easy to get (cheaper brands will not last as long).
Undergravel filters and powerheads
Undergravel filters can be attached to powerheads which are essentially a motor that sits just below the water surface on the top of the uplift tubes. Ideally you would have one powerhead on each uplift tube. The advantage of powerheads is that the rate of water turnover is far greater than with just an air pump. This equates to more effective filtration. Powerheads are also silent.
One other advantage of powerheads are that they are more versatile. Some brands of powerheads also have filter attachments available. This means that the powerhead can be turned into an internal power filter if needed at a later date.
All powerheads have an impellor inside them. This impellor needs cleaning every 6 weeks. If an impellor is not cleaned regularly, then it will need replacing more often (and possibly ruin the powerhead).
Internal Power Filters
The internal power filters have a motor and a sponge attachment. There is no need for a separate air pump. These filters sit about 3 cm below the water surface and plug directly into the electrical socket in the wall. Water is drawn in through the sponge of the filter. They rely on creating a strong jet of water to circulate the water in the tank. It is important that these filters are always underwater when turned on as they rely on the water to keep them cool and will rapidly overheat if turned on out of the water
All power filters have an impellor inside which turns and moves the water through. This impellor can get a build up of dirt, and if it gets too much dirt the impellor stops turning and the filter stops working. This impellor will need to be cleaned every 6 weeks.
The advantages of internal power filters are that they are nice and easy to clean. The sponge will need cleaning every 2-4 weeks, and it is a simple task just to pull out the filter and clean the sponge. These filters are also silent, which many people will appreciate.
Disadvantages of the internal power filters are that whilst they are very good mechanically in removing the dirt and debris out of the water, they are not as good as undergravel filters biologically. There is a relatively small surface area on the filter media for the bacterial population to flourish.
External Overflow Filters
These filters work in a similar way to the internal power filters except that they hang on the outside of the tank and overflow into the tank. They have an intake tube that draws water from down near the bottom of the tank into the filter chamber. Water goes through a sponge and carbon and waterfalls back into the tank.
These filters are the easiest to clean as all filter media are outside the tank, making access very easy. However, not all aquariums can accommodate these filters. Some aquarium hoods will prevent these filters from sitting properly on the side of the tank. Also glass lid supports may be too wide and may need cutting off. And many glass lids will need alterations. In spite of these problems, these filters are very effective at aerating the water, as the waterfall action ensures plenty of oxygen enters the aquarium.
The Aquaclear range of external overflow filters are very versatile in that they contain a sponge (which can be rinsed out and reused) and a carbon bag that come with the filter. It is also possible to purchase Amrid, an ammonia remover, which will fit into these filters.
The other brand of these filters that we stock is the Aqua One range. These have a pull out cartridge with filter wool and carbon. The carbon cartridge should be replaced every 3-4 months.
These filters also contain and impellor that needs cleaning every 6 weeks.
Canister Filters
The canister filters are the most effective of all the types of filters. They consist of a canister that sits underneath the aquarium, usually on the stand or in the cabinet. From the canister filter two pipes run into the aquarium. One pipe is to take water out of the aquarium and down to the filter and the other pipe returns the water. Inside the filter are various filter media, usually a sponge, carbon, and bioballs or noodles. Due to the large amount of media in these filters, a very healthy bacterial population will develop. These filters are also good at mechanically removing debris from the water.
These filters are the most expensive option, however they are also the best. They are particularly good where access to the top of the tank is restricted (eg. built into a wall or cabinet).
Because of the large volume of filter medium these filters contain, a lower hourly turnover is possible, down to 3 times an hour. There is also an impellor that needs cleaning every 6 weeks.
The Heater
If keeping tropical freshwater fish, saltwater fish, American cichlids or African cichlids, a heater will be necessary during winter. Temperatures for most of these fish should be maintained at about 24oC. There are exceptions, notably Discus fish which should be at 28-30oC.
Heater sizes are generally 25W, 50W, 100W, 150W, 200W and 300W. The size heater will depend on the volume of water in the aquarium. It will also depend on where you live. If, for example, you live on the Sunshine Coast, then 1 watt per litre of water is a good guide. Thus, a 50 litre aquarium will require a 50W heater. If the aquarium volume falls in between a heater size (such as 24” = 70 litres), use the next size up heater (in this case the 100W). Larger aquariums (such as a 72” aquarium) may need two heaters. If you live inland (such as the Sunshine Coast hinterland) where it gets much colder at night, increase the heater size by one.
Heaters work by a thermostat. If the temperature of the water is lower than that set on the thermostat, the heater will turn on and a red light will appear. When the temperature reaches the set temperature, the heater will turn off and the light will disappear. It is important to place the heater near the filter, as this is where the most water movement is. It is also a good idea to place the heater on a slight angle. This will prevent the warm water from rising directly onto the thermostat and turning it off prematurely.
ALWAYS have a thermometer in the tank, on the opposite side to the heater, to accurately measure the temperature of the water and to make sure that the heater is working properly.
One common query about heaters why the light is not coming on. The most common cause of this problem is that the temperature on the heater is set lower than the temperature of the water in the tank.
We stock two types of heater. The first is the glass Aqua One heaters. These work on a mechanical thermostat, are fully submersible and have an adjustable temperature.
The second type of heater we stock is the Aqua One Stainless Steel heaters. These have an external temperature control and are made of stainless steel. They are especially good for using in cichlid tanks, but can be used in any tank. However, as with glass heaters, never have them turned on when out of the water. These are stainless steel heaters are unsuitable for use in marine systems.
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