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Revision as of 21:52, 22 December 2007 by Agg (Talk | contribs)



This is the Aquarium Section: Based within Pets & Animals section of OCAU.Wiki. There has been lots of talk about Aquariums, linked with worklogs and many questions across the board. This wiki is to educate those in the know, as well as presenting all of the information you would need to start a tank from scratch. I hope you find this article both informative and interesting and if you have any comments at all feel free to edit the page :)

About Aquariums

An Aquarium is basically a tank (Generally Made of Glass or Acrylic) which is filled with water to keep fish as pets. Tanks can be Freshwater (Non-Heated), Freshwater (Heated) or Marine (Heated). These tanks can house a range of fish from Goldfish to Cichlids, Tetras, Loaches, Pleco's and a wide range of other inhabitants. There is a wide variety of themes, styles and designs which can be implemented to bring your own touch of class to the tank.


The Following is a list of Acronyms that may be referred in this article and / or other webpages:

General Aquarium Acronyms

LFS - Local Fish Shop
FW - Freshwater
SW - Saltwater
DIY - Do it Yourself
HOB - Hang on Back Filter
QT - Quarantine
UGF - Undergravel Filter
HITH - Hole in the Head
LPH - Litres per hour
GPH - Gallons per hour
MH - Metal Halide
RO - Reverse Osmosis
PCF - Power Compact Fluroscent
DI - De-Ionized (Water)
PPM - Parts Per Million

Freshwater or Saltwater?

Size & Volume

How big should i buy?

Calculating Gallons

Calculating Volume (In Litres)

Cabinets and Tank Location



Home Made Stands

Placement and the Effects of Sunlight



The Nitrogen Cycle

A Basic Explanation of the Nitrogen Cycle

Organic matter such as un-eaten fish food, dead plants/fish and fish waste rot in the water and create ammonia. This ammonia is highly toxic to fish and will quickly cause thier death. By using a biological filter, ammonia can be converted into nitrates which - while still toxic to fish - will be far less dangerous to fish than ammonia. As nitrates build up within an aquarium, water changes must be performed to reduce nitrate levels.

The Nitrogen Cycle in Detail

The nitrogen cycle describes the various transformations that nitrogen undergoes in nature. In the context of aquaria, we only deal with the section of the nitrogen cycle that spans from ammonification to denitrification. This article will concentrate on these parts of the nitrogen cycle as used in aquaria. Test kits are availble to measure the levels of ammonia, nitrite and nitrate discussed in this article.

Any dead organic matter within an aquarium such as plant/fish matter, un-eaten food and fish waste will break down with the help of bacteria from organic nitrogen into either un-ionized ammonia (NH3) or ionized ammonium (NH4). There is some evidence to suggest that the PH level of the water effects the type, a PH below 7 results in NH4 while a PH over 7 results in NH3. Ionized ammonium (NH4) is actually not harmful to fish, however un-ionized ammonia (NH3) is highly toxic. For the purposes of an aquarium, NH4 is not considered relevant as it can change into NH3 under common conditions. Therefore this article will only deal with ammonia (NH3) from now on.
A species of bacteria known as Nitrosomonas remove ammonia from the water by a process called oxidation. The by-product of this process is nitrites (NO2-). Like ammonia, nitrites are still highly toxic to fish. Another species of bacteria, Nitrobacter, then convert the nitrites into nitrates (NO3-). While not as dangerous as ammonia or nitrites, nitrates are still harmfull to fish in large quantities. Regular water changes are an effective means of preventing a build up of nitrates in an aquarium. Live aquarium plants will use a small amount of nitrates.
Both Nitrosomonas and Nitrobacter are aerobic, they thrive in oxygenated environments. Some filters (such as the "wet/dry" design) provide an environment where water trickles over otherwise dry media, providing a moist surface with access to oxygen. This is an excellent way to breed both types of bacteria.
For most freshwater aquariums, the nitrogen cycle ends with nitrates being removed from the water through water changes. However, a further section of the nitrogen cycle exists that can be utilised by aquarists to further remove nitrates from water. Several species of bacteria, including Pseudomonas and Clostridium are able to convert nitrates (NO3-) into nitrogen gas (N2) which can then escape from the surface of the water.
These bacteria are anaerobic, they only live in oxygen depleted environments. In salt water tanks these environments can exist within live rock or sand beds. Low oxygen environments in fresh water setups are more rare, however products that can be used as biological filter media and also provide these environments (such as Seachem Matrix) have become availble in recent years. It should be noted that even with live plants and denitrifing bacteria, water changes are still required to keep nitrates at a safe level.

New Tank Syndrome

Many hobbyists new to aquaria can experience sudden losses of many or all fish in a tank. This is often caused by New Tank Syndrome, a spike in the levels of either ammonia or nitrites in the water. These spikes are cause by a lack of any type of bacteria species mentioned above. New Tank Syndrome is avoided by properly cycling a new aquarium.

Tank Cycling

New aquariums using new filters contain only very small amounts of the benifical bacteria required to deal with ammonia, nitrites and nitrates. To aviod New Tank Syndrome (see above), bacteria must be bred inside the tank's biological filter, a process known as "cycling the tank". To start this process, the tank is "fed" ammonia in order to stimulate growth of Nitrosomonas which convert the ammonia into nitrites. Once this species of bacteria has created enough nitrites, futher nitrifying bacteria, Nitrobacter will grow and convert the nitrites to nitrates. Each step in this cycle causes spikes in the levels of either ammonia or nitrites.

There are several methods used in order to cycle a tank, mainly differing in how ammonia is introduced to the tank:

Fish Cycling 
By placing hardy fish in the tank, ammonia can be produced by fish waste. The obvious drawback to this method is the danger to the fish in terms of high levels of either ammonia or nitrites. There are several types of fish that can survive in these tanks, however some people consider it cruel to knowingly keep a fish in toxic water. Some fish used for cycling may not be suitable for the tank in the long term. These are usually removed after a tank is cycled.
Fishless Cycling 
By dosing the water with ammonia or simply letting organic matter rot in the water, a tank can be cycled without introducing any living creatures until the tank is cycled. This method is more time consuming and labour intensive but does not risk the health of fish or force an aquarist to use a fish for cycling that they will later have to remove.

Types of Filtration

There are 3 basic types of filtration needed to clean aquarium water. These are mechanical, biological and chemical. Most filters perform 1 or more of these three functions by use of different "filter media". Examples include bio-balls for biological filtration or sponges for both mechanical and biological.

Mechanical filtration removes large particles of matter such as dead leaves, un-eaten food and solid fish waste. This is usually achieved by using 1 or more types of sponge of varying thickness. Mechanical filtration is often the first type performed on water, as it helps improve the performance of other types of filter media.

Chemical filtration removes many chemicals that are harmful to aquarium fish, as well as removing tannins leached by driftwood. The most common form of chemical media is activated carbon, but products such as Seachem Purigen are becoming increasingly popular.

Biological filtration involves the conversion of ammonia into nitrite and then into nitrate using bacteria present in water. Ammonia is created by the rotting of un-eaten fish food, fish waste and dead plant/fish matter. Biological filter media is defined mainly by it's SA:V, or surface area to volume ratio. Bio-balls or ceramic noodles have been popular for many years, with porous materials such as Seachem Matrix gaining popularity in recent years.

For more infomation, see The Nitrogen Cycle.

Under Gravel Filters

Hang-on Power Filters

Internal Power Filters

External Canister Filters

Sump Setups

Air Stones / Air Bars / Powerheads

Airstones, air stone bars, powerheads do not provide filtration. They provide water circulation for your tank which may help deliver oxygenated water into the deeper levels of your tank where oxygen can not freely dissolve into. Oxygen only freely dissolves into around the top 5cm of your tank water, so moving this oxygenated water into the deeper levels of your tank will ensure oxygen is made accessible to all creatures living in your tank.

Although they do not exclusively provide filtration, the use of air stones and powerheads can supplement filtration. The use of air stones and powerheads to move water through sponge filters and undergravel filters will provide water circulation to grow beneficial bacteria on your filter media.


Freshwater Lighting

Marine Lighting

T8 Lighting

T5 Lighting



Compact Fluro

Metal Halide


Heating is a very important part of fish keeping. Although it is commonly thought that fish that live in water around room temperature can be left in tanks without heaters, temperature regularity is as important or even more important than the relative water temperature. Temperature fluctuations due to ambient air temperature around the tank will cause tank water fluctuations which will cause discomfort and stress to your fish and at extremes will cause illness. Heaters prevent temperature fluctuations by monitoring water temperature and heating as necessary. There are different types of heating available. In general you get what you pay for with heaters. Getting cheap heaters is okay for temporary situations but their reliability may be questionable in the long run. Non submersible heaters are not recommended as they are obviously sitting in water, if water gets into your heater it may cause a short circuit. Heaters are usually factory adjusted, though they may not necessarily be accurate for the adjusted temperature. Make sure you have a thermometer in the tank with your heater so make sure the set temperature is the temperature you want. If your tank is constant for the wrong temperature then make adjustments to the heater as appropriate to heat to the needed temperature.

CO2 Injection


Professional Setups












Feeder Fish














Sword Tails

























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