Biological Filtration

From ReefPedia

Contents 1 What is biological filtration? 2 How Long? 3 The Natural Alternative 4 Testing 5 Biological Media 5.1 Care of the media

What is biological filtration?

Once you have set up your new tank and you are pleased with the results all you now need is to add the fish. The dealer who sold you the tank probably said to leave the tank without fish for a few days or even a week in some cases and then it will be ok to add the fish. The above piece of worthless advice has killed more fish than probably any other single thing in the hobby and has also probably led to countless people giving up before they have even properly started because no matter how long the tank is left to stand it will not mature on its own.

Fish produce and excrete ammonia from their waste. This waste will quickly pollute the water and ammonia is toxic to fish at incredibly low levels: just one part in five million is enough to kill some fish and to make others very ill. Fortunately, there are several groups of bacteria which act together to get rid of the waste and ammonia on our behalf and to make the tank a safe place for fish to live. However, it takes time for the numbers of these bacteria to build up to a sufficient level for them to be able to deal with all the ammonia and waste and before they have reached that level the tank is said to be immature or un-cycled.

How Long?

It can take a 8 to 10 weeks for the aquarium to become fully cycled but leaving it completely empty will not help because for the process to begin the helpful bacteria have some requirements of their own before they will start to colonize the tank. First, the tank should be allowed 48hrs with everything running so that everything can be seen working the temperature can finely tuned, filter outputs can be directed to make a gentle current run throughout the tank and the decor can be placed to conceal equipment.

After 48 hrs the maturing process can begin, in times gone past we used to add six cheap disposable fish to the tank so that they would produce ammonia and other waste. Then the Nitrifying bacteria (chemoautotrophic bacteria that grow at the expense of inorganic nitrogen compounds) specifically called nitrobacteria and nitrosoma, which are actually living on the fish themselves, would then feed on this waste until there were enough bacteria spread throughout the tank to maintain a healthy water quality. But this meant exposing the unfortunate first fish to very high levels of toxins which often resulted in their death, this is a very poor method to use and is totally unnecessary not to mention unethical.

Another method is to add small pieces of fish or shrimp. This will produce lots of ammonia for the bacteria to feed on and they will colonize the tank without harming any fish in the process. For the typical 55 Gallon tank, roughly 4 grocery store-bought 3 inch shrimp will be enough to begin the nitrogen cycle and produce enough ammonia to feed and grow an initial load of bacteria. The bacteria does not have to be added to the tank (it comes with the shrimp), but the use of live sand inoculated with a culture of bacteria can decrease time needed initially cycle the tank. Using this method, no higher life forms should be in the tank; the high concentration of ammonia and nitrites produced will kill most animals including those inhabiting live rock.

It is now possible to buy products from aquatic stores which provide the ammonia in a clean form and they contain other chemicals like trace elements and nutrient which create an ideal environment for the bacteria. This is just a random example and shouldn't be taken as a recommendation for this particular product. Do not confuse this type of product for one which claims to add live bacteria to the tank and mature it instantly because many of these products simply are very ineffective and a waste of money.

The Natural Alternative

It is now known that there are a number of methods which can cycle a tank in as little as one day Naturally. The two most common ways are:

Cycling with Live Rock

Adding Live Rock, that was harvested from the Ocean, or another established tank will introduce the proper bacteria immediately to your system. It is suggested that you have approx a minimum of 1 lbs per inch of fish. It would be better/more stable, and safer for you to add more live rock. Why Add live rock? Well this sets up a miniature Ecosystem in your tank, which is MUCH more stable than simply adding the nitrobacter and nitrosoma, from the fish themselves. Plus you will need tank decorations anyway, and Live rock is more bennifical, as it adds a natural food source, in the form of Amphipods, copopods and isopods. Live Rock can serve as the main base for biological filtration in a saltwater aquarium, while the organisms on it will help consume organic matter. Systems with LIVE ROCK, will culture non-living coral sand in a setup over time. Systems set up this way are commonly called Berlin style systems. (although a TRUE Berlin method system has no sand or substrate)

NOTE: Cold water live rock, ie. from the coast of california will NOT work for Tropical salt water applications.

Cycling with Live Sand

Live Sand or LS is natural reef coral sand that is collected live from the ocean, or non-living coral sand that is cultured in an already established system. What makes it live is the microscopic biological bacteria that grows on it, and the Amphipods, copopods and isopods, and other micro / macro-organisms that live and breed within it. Live sand can serve as the main base for biological filtration in a saltwater aquarium, while the organisms help consume organic matter in the sand bed. Systems with LIVE ROCK, will culture non-living coral sand in a setup over time.

NOTE: If LIVE SAND is being sold to your in a pre sealed plastic bag (available in some stores) It is not LIVE SAND REAL Live sand deprived from oxygen, and water circulation will turn black in color from the anaerobic bacteria overpopulation. and will have a strong smell. (normally small amounts of anaerobic bacteria are present, and are actually positive additions because they convert NO3 into nitrogen gas, which gets rid of nitrate)

Which ever method you choose, as soon as the process has begun changes will take place in the aquarium and in the water chemistry in particular. The bacteria which are present will begin to multiply rapidly and start to consume the ammonia the ammonia is converted into nitrite and the nitrite into nitrate how and why they do this isn't really important the important thing to remember here is that both ammonia and nitrite are deadly to all fish but nitrate at the end of the process is relatively harmless except in very high levels.

Testing

You can monitor the changes taking place but to do this you will need a few test kits. The test kits themselves are a very important tool to use when keeping fish and some are indispensable - a test kit for each of the following should be considered as mandatory if you are to become a successful fishkeeper,

• Ammonia test kit.
• Nitrite test kit.
• pH test kit.

There are of course many others which are useful (see category:Test Kits but the three are essential for knowing when a tank is cycled (and therefore safe for your livestock).

A newly filled tank will probably show 0 on all those test kits but a few days into the maturing process will show a dramatic rise in the ammonia levels but still no nitrite or nitrate. After a week has passed the ammonia levels will have peaked and may have declined a little whilst the nitrite levels will show a rapid rise but there will still be little or no nitrate. The reason for the time difference in these processes and why they don't all rise and fall together is because different bacteria are responsible for each process and the different bacteria grow at different rates.

The ammonia will then quickly disappear altogether but the nitrite levels will remain quite high for quite some time up to 35 days is quite common although it often drops more quickly than that. It is simply a matter of waiting and keep testing. eventually Nitrate will begin to appear and shortly after this the nitrite level will start to fall. Once it has fallen to 0 the tank is cycled and the first few fish can be added. It is very important with a newly cycled tank that the fish are added slowly and not all at once and allowing at least one week for the new fish to settle before adding anymore fish to the tank, this is to allow the bacteria colony time to adjust to the stocking level.

Biological Media

The photo on the right is of some pieces of Siporax which is made from sintered glass. It has a massive surface area because it is made up of very tiny pieces of irregularly shaped glass with lots of microscopic nooks and crannies for the bacteria to live on and because of the tubular shape of it, it never becomes blocked up which makes it ideal for use in external power filters. Once mature it simple needs the occasional rinse in old tank water and it never needs replacing. The sponge in a filter also allows bacteria to colonise it and makes a very efficient media for biological filtration once it has been matured A close up of the surface showing that it is made from tiny pieces of glass. The helpful bacteria can actually enter inside the Siporax in between the bits of glass making the whole piece alive with it's own bacterial colony. A few of these mature pieces can be removed and placed in a new filter with new Siporax and it will very quickly seed it and speed up the maturation process.

Care of the media

Once the media is mature it needs to be treated as a living thing and a vital part of the aquarium.

The media itself isn't alive but every single bit of the surface of it will be colonised by bacteria and the health and well being of all the aquariums occupants depend on this bacteria. Just like the fish the bacteria have needs which must be met if they are to thrive, primarily this means food and oxygen. The fish will provide all the necessary nutrients and the bacteria will adjust their numbers to suit the available food. But in order to keep the waste from the fish from polluting the water a good supply of oxygen is required so the media must not be allowed to become blocked up with dirt or the water flow will be reduced which in turn means the oxygen supply will be reduced. When cleaning the filter use water taken from the tank to clean the media because water from the tap contains chlorine which has been put there to kill bacteria. During filter maintenance there is no need to make the biological media spotlessly clean but just ensure that there is a good water flow through it.

   Original article contributed by Fish Tanks and Ponds