Buffering Seawater

Marine livestock are used to very stable conditions. Much of this livestock comes from the wild reefs and there are literally cubic miles of seas and oceans to act as a sump. True, reefs can have problems created by mankind, such as industrial and agricultural run-off etc. This pollution has occurred over the short term, reef life has become used to very stable conditions over a very long period.

There are increasing numbers of locally produced corals and fish. These demonstrate a little more flexibility when faced with varying conditions because they have grown in an aquarium. Nevertheless, stability is a need for success with all livestock from whatever source.

The seawater is the area where this stability is of major concern, particularly in reef aquariums. In a fish only system the basic parameters need to be monitored, and in a reef a good few more. One of these is the buffering capacity of the seawater.

There isn’t any mumbo-jumbo on its way, the subject is straightforward and of importance to the reef aquarist.

A very quick look at pH first. pH is the measurement of acidity/alkalinity, and uses a scale of 0 to 14 (0 is acid and 14 is alkaline). Neutral is 7. Aquarium seawater can be between 8.0 and 8.4, with 8.2 or 8.3 often quoted as ‘perfect.’ So it can be seen that the seawater is on the alkaline side.

Life in the aquarium through its normal functions, feeding and the breaking down of dead algae etc puts pressure on the pH. This pressure continuously attempts to move the pH towards the acidic side of the scale. If the pressure has an effect on the seawater the pH will begin to drop. The pH will remain stable, at least for a time, because of the buffering capacity of the seawater. This ‘buffering capacity’ is also known as alkalinity and carbonate hardness. What happens is that the acids produced are negated by the ‘bases’, these are mainly bicarbonates and carbonates. Thus the pH remains stable.

The buffering capacity is finite. One way of boosting it is to complete regular seawater changes, though this in itself will not guarantee a continuing stable level. Sometimes it is necessary to engage supplements which are available from commercial sources. Supplementation should not be undertaken until it is certain the aquarium needs it. A slight fall in the level throughout a week or a fortnight which is repetitive is not a problem; this can be seen by the use of test kits. If the aquarist is having problems maintaining a steady pH or a proper level of calcium for example, scrutiny of the buffering capacity is in order. (Calcium should be in the area of 400 to 450 parts per million.)

In the aquarium it is considered beneficial to maintain the alkalinity a little above natural seawater levels because of the limited gallonage available. The level can be measured in meq/l or dKH. Any one is fine and the test kit will advise which scale is being used. They come to the same thing.

The levels recommended are 2.5 to 4 meq/l, which equates to 7 to 11 dKH. As said there isn’t a need to worry about the measurements, just go with what the test kit offers. Try and use a good test kit – questions on forums or to other local aquarists should produce recommendations.

The needs of a particular reef aquarium will soon be known and maintaining alkalinity becomes quite simple. Desirable algae, corals, snails etc will all benefit.

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