Many beginning hobbyists often lose fish when first establishing an aquarium, which is generally referred to as "New Tank Syndrome". Newly established aquariums need time to establish a natural biological cycle (Fig. 1) and fish mortalities can occur during the establishment of this cycle of bacterial activity. It is not critical that you understand the intricate metabolic process that naturally occurring bacteria use to create and maintain this cycle. However, a reasonable knowledge of the major steps of the cycle and what effect, it has on water quality is required.
The ability to maintain rainbowfishes in good health is a function of the efficiency and health of the aquarium's biological cycle and the aquarist's management of the system. When establishing a new tank, adequate numbers of bacteria must be present to maintain a biological balance. Bacteria are present everywhere and reproduce at astonishing rates and are the most important biological converters of organic wastes to new elements and gases. Bioconversion or decomposition gradually removes organic wastes and is facilitated by providing and maintaining an optimal environment for the appropriate bacteria. If the appropriate bacteria are not present or if the correct physio-chemical conditions are not maintained, the biological cycle will not function adequately. When this happens the fish will be stressed, and can even die. Nitrifying bacteria generally thrive in a pH range from 6.5 to 8.5 and will not survive at a pH of less than 4.3 or above 10.5. It is important to note that nitrifying bacteria require oxygen to function. If oxygen levels are not sufficient, the process can break down.
During the time it takes the biological cycle to become established ammonia levels can get very high. Several days after reaching their peak level, ammonia-consuming bacteria convert them to nitrite. As ammonia levels begin to fall, nitrite levels begin to rise and continue to rise for some days until nitrite-consuming bacteria levels are sufficient to consume the nitrite and convert it into the relatively harmless nitrate. This cycle is generally referred to as the biological cycle or nitrification.
Prior to stocking the aquarium it is advantageous, although not absolutely necessary, to pre-activate the cycle. Pre-activation is accomplished by seeding the filter(s) with nitrifying bacteria (available commercially) and providing a synthetic growth medium for a period of 2 weeks. There are many products on the market today which claim their usefulness for this purpose. However, care must be taken to understand the nature of the products and often what is not stated on the labels or perhaps not even understood by uninformed manufacturers. Some commercial products contain bacterial soup while others have an ammonia-based composition. I suggest you use one of the ammonia-based products that contain a source of ammonia (10-20 mg/L), trace elements, and a buffer. Bacterial products are somewhat over-rated and in fact, some claims are erroneous.
It is best not to add any fish to a newly established aquarium until the biological cycle has been established and ammonia and nitrite levels are zero. This requires variable lengths of time, but it should generally be safe to start introducing fish after 21 days, but use test kits to monitor the process. All hobbyists should have an ammonia and nitrite test kit and know how to use them.
© Copyright Adrian R. Tappin
Updated October, 1999.
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