Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish




Getting the filtration right is probably the most important thing in fish keeping of any sort. There are three main types of filtration and these are:
Mechanical filtration which is the removal of suspended solids from the water column making the water clear and pleasing to the eye.
Chemical filtration where dissolved solids are removed either by absorption or adsorption using filter media like carbon.
Biological filtration where bacteria are used to oxidise ammonia and nitrate into the less harmful nitrate. This is by far the most important of the three and is essential to the wellbeing of every aquarium.

Types of filter

There are quite a few options available for filtering an aquarium, here are some of the most popular ways.

Under gravel filter:

Are less popular than they once were because they have some major drawbacks when compared to more modern filters. They are essentially meant for biological filtration alone and can't be used for mechanical or chemical filtration. They have some major advantages too, they are very efficient, cheap and easy to conceal. They work by drawing oxygenated water through the substrate allowing bacteria to build up on every surface in the entire substrate. This is a massive surface area and as long as the substrate is well maintained and kept clean there are few better biological filters.

Advantages - Very cheap, no moving parts so nothing to break, extremely efficient if well maintained, almost totally hidden when in situ, silent.
Disadvantages - The substrate can become blocked with dirt if not properly cleaned on a regular basis. Doesn't have any facility for chemical or mechanical filtration.

Internal power filter:

This type of filter can fulfill all three types of filtration and is easier to maintain than an under gravel filter. Not quite as efficient as the under gravel filter when it comes to biological filtration but is still more than capable of providing sufficient biological filtration to meet the needs of most aquaria.

Advantages - Easy to maintain, offers a wide range of filtration options, reasonably priced.
Disadvantages - Difficult to conceal and retain access, small size limits options.

External power filter

The most popular filter in use today. External power filters have a large capacity, there is nothing to hide in the aquarium and they offer a very wide range of options. It is easy to in-cooperate all three types of filtration in an external power filter due to their size and the fact that there are separate media containers within the one filter. This is probably the best option for most situations.

Advantages - Easy access, nothing to conceal in the aquarium, easy to maintain, very efficient.
Disadvantages - Relatively expensive.

Protein skimmer

This is a device which really works best in salt water aquariums. As waste is broken down by fungi, bacteria and protozoa it goes through many stages before it becomes ammonia. There is a stage where large molecules form which have a property which the protein skimmer can take advantage of. The molecules are hydrophobic at one end and hydroscopic at the other end. This simply means that one end is attracted to water and the other to air. By passing millions of tiny bubbles through these molecules the end that id attracted to air sticks to them and as the bubbles rise they take these molecules with them where they form a scum at the surface. The protein skimmer separates this scum from the water and collects it where it can be disposed of. This means that a lot of the biological waste is removed before it becomes ammonia and ultimately nitrate which means the water quality is better maintained for a longer period of time.

Filter maintenance

Correct maintenance is essential if you are to get the best out of your filter. For under gravel filters the main thing is to keep the substrate clean, this involves more than just simply dragging a siphon pipe over the surface, you have to really stir up the substrate and then let the mulm settle and then siphon it away. If the landscaping of the tank prevents you from doing this then the under gravel filter shouldn't be used.
Maintenance for an internal power filter and an external power filter is similar. Any chemical filter media such as carbon needs to be replaced at least every four weeks, ion exchange resins need to be recharged or replaced. The very fine filter matting used for the final stage of mechanical filtration should also be replaced. The most important part is the cleaning of the biological media whether it is sintered glass, sponge or other media. It has to be cleaned by rinsing in some water taken from the tank and never rinsed in tap water. The chlorine or chloramines in tap water will kill the bacteria and that would lead to water quality problems. The biological media doesn't have to be cleaned until it is spotless either. Just rinse it enough  to ensure that water can flow through it easily.

Maturing a filter (cycling)

What actually happens when you mature an aquarium?

It is bacteria which maintain a healthy environment for fish to live in. They are responsible for breaking down all organic waste and rendering it harmless. These helpful bacteria have to be encouraged to colonise a fish tank before it is used to house any fish or the health of the fish will be at great risk. This is a very common problem among new fish keepers and the condition is commonly known as "New Tank Syndrome".
Fish produce ammonia and are constantly releasing it into the water column, they also produce waste which various fungi and bacteria breakdown into ammonia, this ammonia then builds up in the water until it reaches lethal levels and kills the fish.
To combat this problem we use a bacterial colony mainly housed in the filter which breaks down this ammonia into nitrite and then into nitrate which is RELATIVELY harmless.

The filter bacteria

The different species of bacteria involved in the process have different needs and they colonise the filter in stages. The first to make an impact are the bacteria which breakdown organic waste and produce ammonia. This leads to a rapid increase in the ammonia level in the water because there are no bacteria present to break it down yet.
Once there is a good level of ammonia in the water the next group of bacteria begin to colonise the filter, these bacteria use the ammonia and produce nitrite. Nitrite is also extremely toxic to fish and when both ammonia and nitrite are present at high levels then the fish are unlikely to survive.
Once there is a good level of nitrite present a third group of bacteria begin to colonise the filter, this group use the nitrite and produce nitrate which is the end product of the nitrogen cycle and is the least toxic. Nitrate levels are normally controlled by making regular partial water changes using nitrate free water.
Even when all the ammonia and nitrite are being dealt with by the filter bacteria the maturing process will continue for the next few months. Using the example of the three species of bacteria which turn waste into ammonia, then ammonia into nitrite and finally nitrite into nitrate is a very much simplified version of what really happens. There is a whole mini eco system at work involving virus, bacteria, protozoa, fungi, single celled creatures as well as flat worms. round worms and so on all of which play a part in breaking down the waste. This eco system takes a while to reach a balance and mature and so even after the tank appears mature and is holding a good fish stock, the maturing process will continue.

Once fully mature and well maintained a fish tank should have few problems.

What do I have to do in order to mature the aquarium?

When you fill the aquarium for the first time it will be relatively sterile. in order to help the process to begin you will need to add a source of ammonia.
Although the following methods differ in their approach they are all simply variations on a theme. Ammonia is added in some form, the bacterial colony grow and the tank becomes mature (cycled).

Method one (a) - The easiest and most simple way to mature any aquarium. *Recommended
Use Waterlife's BioMature as instructed. This product contains all the ammonia that is required. Simply add the required amount on a daily basis until the nitrites reach between 5 to 10mg/l and then stop adding it. Keep testing the nitrite level which will remain stable for a while and then it will suddenly drop. Once it reaches 0mg/l the tank is matured. That's all there is to it.
People sometimes get a little confused with this and worry about the bacteria dying off if nothing is added while waiting for the nitrite to fall. Well, there is no need to worry because the bacteria remain healthy, there really is no need to keep adding more and more ammonia once the nitrite level is between 5 - 10 mg/l. You don't even need to measure the ammonia level. Tanks normally take around two weeks or less to mature using this method.

Advantages: Very easy to do, only requires the nitrite to be tested, clean and efficient, you have full control of the process, no fish are harmed.
Disadvantages: Supermarket ammonia is cheaper if you have several tanks to mature.

Method one (b) - An even faster method - If you have a mature fish tank already then taking about 1/3rd of the mature biological media out of the filter and incorporating it in the new system and then proceeding as laid out above to mature the tank it will be a much shorter maturing time, often less than seven days.

Advantages: Very fast.
Requires access to a mature aquarium.

Method two - Ammonia from a bottle

The internet method. Instead of using a purpose made product like the previous method this one uses supermarket bought ammonia. Ammonia is added until the level in the aquarium reaches 4mg/l. I don't know if 4mg/l is the optimum level or not but it is the level which is most often quoted.
Add ammonia as and when required to maintain a level of around 4mg/l. After a short time nitrite will begin to appear and the level will rise. Eventually the ammonia will fall to 0mg/l within a 24hrs period and sometime later the nitrite level will do the same. Once both are falling to 0mg/l within 24hrs the tank is matured and ready for fish.

Advantages: Cheap (useful for a new fish house or large tanks).
No fish are harmed.
Disadvantages: No real information is available, just hearsay from those who have tried it.
Ammonia is quite a nasty chemical to handle. It is no cheaper if you only have one tank to mature since you will have a lot left over (wasted).
Requires that both ammonia and nitrite are tested regularly. Takes longer to mature a system. Nothing other than ammonia is added so extra buffers may be needed.

Method three: using  fish, meat or prawn as a source of ammonia.

Meat, fish or prawns can be used to produce ammonia by placing a few of thumbnail sized pieces in the tank and leaving them to rot, they will need replacing periodically because they contain a finite amount of ammonia.
It will take a little while for the process to begin and it might be a few days before any ammonia can be measured, again using this method a level of 4mg/l of ammonia should be aimed for by either adding more or removing some of the ammonia source. Keep adding new pieces of meat, prawn or fish so that the ammonia level is maintained, eventually the ammonia level will fall and the nitrite level will rise until it reaches a peak and then that too will fall.
Once the levels of ammonia and nitrite are at 0mg/l the tank is cycled. It should then be given a good clean to remove all the debris and then a partial water change before adding any fish.

Advantages: This method is more likely to produce a more complete cycle if done correctly.
May eventually lead to a more natural and complete filter media flora and fauna being established.
No fish are put at risk.
Disadvantages: Using this method is more difficult because it isn't very controllable, the ammonia may end up being to high or to low and slowing the cycle down or it may never reach a level which builds up a large enough colony of bacteria. Dirty, the remnants of the ammonia source will need removing once spent. Columnaris bacteria can grow on this material and it can cause illness to fish at elevated levels. This is one of the slower methods and may take considerably longer than other methods.

Method four - cycling with fish. *Not recommended

Cycling with fish is possible and it can be done without any risk to the fish. A large aquarium is the best option for this method because the initial stocking levels must be very low or the fish will be at risk. The fish will produce ammonia as soon as they are in the aquarium and as soon as ammonia is present the maturing process will begin. The theory behind this method is that the ammonia levels will be kept dilute in a large volume of water with very low stocking levels and that the ammonia levels will begin to fall again before they reach a level which is uncomfortable to the fish.
Feeding has to be kept low and tank maintenance has to be good so that neither ammonia or nitrite levels never rise above 0.1 - 0.2 mg/l. A 50gall tank with around 3 or 4 small tetras would achieve this, a 12gall tank with two goldfish would not and the goldfish may not survive.
Stocking levels can be very slowly built up by adding a few new fish when no ammonia or nitrite can be detected until the desired stocking level is reached.

Advantages: Fish are added to the tank relatively quickly.
Disadvantages: If to many fish are added at once then they are very much at risk. If it is done wrongly then it involves a great deal of cruelty. This is a very slow method when compared to the others. Only likely to work with large aquariums housing small fish. Both ammonia and nitrite levels have to be checked very frequently, water changes may be called for if the levels begin to increase to much.

Method five - maturing a planted aquarium

By planted aquarium I mean a specialist set up with CO2, special substrates and the right lighting levels for plant growth and most importantly - densely planted with healthy and actively growing plants.
I do NOT mean a normal aquarium with a few bunches of plants pressed in to the gravel.
The plants will take on the role of the filter bacteria to begin with by removing the ammonia from the water in order to use it for themselves. Lots of actively growing plants will have little trouble in doing this although there will still be enough left over for the tank to mature in the normal way, Quite often this is the only method to use on such a system because the plants remove the ammonia so efficiently that other methods of adding it will fail.
Fish stocks should be built up slowly in order to play it safe and to keep the fish healthy.

Advantages: Once the plants are settled in and growing, the fish can be added. Generally a very safe method to use.
Disadvantages: Requires a specialist planted aquarium.


  1. Will aquarium disease treatments affect the cycle?

    Yes, although many products claim not to harm filter bacteria, most will set the cycle back a little if used. It is best not to use them in a maturing aquarium if at all possible.
  2. Will the pH of my aquarium make any difference to the maturing process?

    Yes, all the different species of filter bacteria thrive better in water which is slightly alkaline. Ideally pH 7.6 to 8.5 once mature the pH can safely be adjusted to suit the fish.
  3. Does temperature make any difference to maturing an aquarium?

    Temperature makes a tremendous difference. When the maturing process is going on if the tank is kept in the mid eighties F the process will be very much faster and the tank could mature in as little as two weeks.
  4. Will adding ammonia to my tank occasionally help keep the filter in tip top condition?

    Ammonia must never be added to a tank containing fish. It could kill them.