Success Aquaria employ science

A passion which has grown into a profession for Mr. Abhik Mazumdar* who is a lawyer by profession.

To many people, an aquarium is about putting some colorful fish into a glass tank with water, and throwing in some food everyday, on the assumption that the fish will fend for themselves completely. When the water seems too dirty, they change it. If the fish seem abnormal, they put in a profusion of dyes which are "medicine" as per the fish dealer consulted. If fish die, then they will be replaced, since they are disposable commodities. To compound the problem, there is a distinct lack of good aquarium literature in the country. Whatever expensive imported book on the subject is available mostly talks about methods which are not very practical in our country given the lack of good dealer support and unavailability of drugs and equipment. So the trial and error methods continue.

This approach is most deplorable, because, fish and other aquatic creatures, just like all of us and our other pets, require good hygienic living conditions. It is only common sense which can tell us, that, in fact, unlike terrestrial creatures, fish constantly live in a medium (water) which also carries the waste produced by the animals in it, including urine and faeces. No animal is designed to live like this. To successfully address this problem, apart from physically cleaning the water, there has to be a sewage treatment mechanism of sorts in place so that the nitrogen cycle is in place inside the tank. This is the very basic minimum requirement of keeping aquatic creatures successfully in the long run. Such a scientific approach is the basis of this series of articles which will strive to teach the serious aquarium hobbyist how to keep his fish. The balance of the biological system in the aquarium is dependent on the decomposition and utilization of waste materials. This cannot keep going unless we control and interfere in facilitating the same. Specific measures have to be taken for the removal and decomposition of waste materials/ minerals. While water changes fall into the category that removes waste materials, this is not the key to the problem by itself. We have to understand that by constantly changing water, we are still far from duplicating nature. We may improve the living conditions of aquatic creatures temporarily, but we are also subjecting them to frequent large environmental shocks that stress them in the long run. Your fish may certainly look rejuvenated initially, because, no doubt the changed water is better that the sewer (excuse the strong term!) it was living in just prior to that, but it is never really able to adapt and settle down properly because other water parameters such as pH, alkalinity, hardness, levels of dissolved solids, nitrates etcetera can vary widely as a result of drastic water changes. Water changes should be carried out in smaller percentages of total aquarium water, as per schedule, only as a supplement to good aquarium sustenance techniques.

Thus, while removing a considerable part of these materials from the aquarium through water changes (we will realize which waste materials are addressed by water change techniques after we study the nitrogen cycle), we must also support the work of the organisms which decompose these materials in nature (again a study of the nitrogen cycle will reveal that most of the initial waste products need to be addressed by supporting such natural decomposition ahead of water changes).

Nitrogen Cycle and its relation to Oxygen

Vertebrates produce metabolic waste invertebrates. Ammonia, ammonium, urea and uric acid are common products of excretion. These products have one common factor..... they all contain nitrogen. Dying and decaying algae, food substances, etc. all contribute to these wastes in an aquarium. Here nitrogenous compounds occur in the form of proteins. Proteins /albumens and such like other complex compounds also accumulate as organisms decay.

Oxygen is indispensable for most living creatures, and yet it is not available everywhere. Apart from its most basic function of allowing any animal to respire, oxygen has another very important role in aquatic environments for the establishment of the nitrogen cycle. A milieu where oxygen is available is called aerobic, and if there is no oxygen, it is called anaerobic. Most free moving water is aerobic, whereas, conditions in the bed as well as inside porous rocks could be anaerobic. The bacteria which are absolutely central to all underwater environment are aerobic and anaerobic bacteria which control the complete nitrogen cycle, creating the base for the establishment of an eco­system.

It is not possible to address in depth the chemical reactions involved in the scope of these series, but it is enough for the hobbyist to be aware of the following chain of waste products and by-products:

• Urine and faeces

• Amino acids + Uric acid 

• Ammonia/ Ammonium 

• Nitrites

• Nitrogen + Oxygen.

Aerobic (that is, oxygen loving) bacteria that live in oxygen rich surroundings break down the waste products to the level of the nitrates. After that anaerobic bacteria that have to be maintained in surroundings devoid of oxygen need to be used to break down nitrates into the logical end products of nitrogen and oxygen. It is the work of aerobic bacteria that we need to support the most, because the toxicity of ammonia and nitrites in water high and they act fast, killing fish. Ammonium, as a matter of fact, immediately occupies the gills of fish to the exclusion of oxygen causing rapid death. Thus the removal of these products cannot be left up to water changes. The aquarium must be equipped to at least convert all waste products into nitrates. Nitrates can then be removed vide regular water changes because it takes a long time for toxic levels of nitrates to accumulate in the tank. Of course, specialist aquaria that are complete ecosystems incorporate denitrators to remove nitrate also but that is outside the scope of the normal hobbyist, and such methods are mostly left up to advanced hobbyists typically having marine reef aquaria.

As mentioned earlier, aquarium fish always require high levels of dissolved oxygen in water (with the exception of a particular group of fish called the labyrinth fish.....a topic which will be dealt with much later) for respiration, but now it becomes clear that certain bacterial species central to the success of the aquarium also need to be supported with oxygen. While we will deal with how these are to be maintained later in this series, it is important at this stage itself to note the importance of available oxygen in aquarium water. It is also to be noted at this stage, that many aquarists observe their fish gasping for breath at the surface, and sometimes also dying in the process. They are usually able to understand that oxygen is deficient, but are also usually erroneous in adjudging the cause for such deficiency. One common cause of oxygen deficiency, unknown to many hobbyists is rising and high temperatures because the capacity of water to dissolve oxygen goes down as temperature rises. Thus on many occasions the same tank that is supporting a number of fish, fails to support the same number when it becomes hotter. This is the reason. I add at this stage that I have not yet addressed the remedy or the equipment necessary in a healthy tank. That will come much later. Here I just wanted to put you through the theory and the causalities of oxygen and the nitrogen cycle.