Some notes on water qualities and treatment for Rift Lake Cichlid Aquaria

 

The cichlids in Lakes Malawi and Tanganyika have evolved in a chemically very stable environment.


The seasonal effect of rains and run-off of top soil into a lake as big as Tanganyika, which holds around one sixth of all the fresh water on the planet, is minimal when compared to the variations in water quality in river systems. While anecdotal evidence exists of rift lake cichlids being kept successfully in soft, acid water, I would not recommend such a practice. This is because no member of this group of fishes has encountered such water conditions in nature throughout the course of their development over, in the case of Tanganyika, millions of years. Therefore any gene variations that would benefit an organism in such variable conditions are likely to have been lost, as there has been no benefit to be derived from such abilities over the course of their development from the earliest
times in the lake to the present day.

The original cichlid populations in the large lakes will have come from elsewhere and therefore from more variable water systems. It is a safe assumption that these fishes would have been able to cope with the big changes in water chemistry they would have encountered in the seasonally variable river systems and smaller lakes in which they had developed. As generations passed in the new, stable lake environment, the genetic advantage of this ability will have become an irrelevance, with no advantage gained by individuals which retained it.

The contrast between this and the conditions in which those cichlids that have evolved in coastal regions, such as Etroplus, is probably the easiest way to understand this point. Fishes moving from fresh to brackish and even salt water are coping with very large changes in 'osmotic gradient': in fresh water the inside of the fish has a relatively high concentration of salts, and the body system must be adapted to expel excess water which enters the body through osmosis. In salt water, the reverse is true: water will have a tendency to move from inside the body, where the concentration of salts is lower than that of the surrounding water, to the outside environment. Etroplus therefore have retained this ability: any genetic mutation in their history which lost the ability to regulate the body's systems in both fresh and brackish water would have been a genetic dead-end - the individuals could not survive in their environment without it.

The relevance of the above argument for keepers of rift lake cichlids is that we should not impose unnecessary and unnatural stresses on the internal regulatory systems of the fishes we keep. As these fishes have evolved in such chemically stable ecosystems, we should do our best to provide similar chemistry and stability of the systems in which we keep them.

By providing such conditions we aim to allow the fishes to live out a relatively 'normal' life pattern (as much as it can be in an aquarium setting) in good health. Give them unsuitable water and their regulatory body systems will be in a constant struggle to maintain a healthy equilibrium, and as explained they simply have not evolved to deal with this. The result is likely to be unhealthy fishes, constantly struggling to maintain bodily equilibrium while not properly equipped to do so.

We would not expect tropical fish to survive in cold water: the reasoning is the same. The fish have never encountered such conditions in the course of their development, and so can be expected to lack the regulatory body function to cope with such variations in the environment.

Therefore, if your water is soft and/or acid, it makes very good sense to adjust the water parameters to make it more suitable for your rift lake cichlids. If you are lucky enough to live in an area with hard water and a pH of more than 7.2 then water treatment is probably not required but I would still recommend the use of buffer substances, either in the tank decor and/or substrate, or as filter material. Suitable substances are tufa rock (can be unsightly, however), chipped limestone, calcified seaweed (the best I have found when used in a filter or by mixing a few handfuls with your substrate) or coral sand used in the filter - I advise against using this material as tank substrate (see Tips page).

Buffer materials will protect against sudden drops in readings caused by filter failure, unexpected changes to mains water, etc.

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Water in my set-up
My fish room has now been closed down, but I have kept the description below on the water treatment regime I used, for information.

The Water
pH is around 7.6
Carbonate hardness (KH or TAC) is around 9°dKH (161 ppm)
Total hardness (GH, DT or TH) is around 8°dGH (143 ppm)
Nitrite nil
Ammonia nil
Nitrate <20ppm

The mains tap water here is pH 7 with no hardness reading at all.

In my fish room set up, two 37 gallon (165 Litre) reservoir tanks are set at the highest level on the top of four-tier stands.

Mains water is piped direct to these tanks.


For water changes, the tanks are filled from the mains, and the following added to each 165 litre tank:

9ml API Tap Water Conditioner (480ml for £8-£10 treats around 1850 gallons)
45g of Sodium Bicarbonate (local Chinese Supermarket is cheapest)
30g of Epsom Salts (Magnesium Sulphate)

These mineral salts achieve the pH and hardness figures given above. Note that the API Tap Water Conditioner is used at the high dosage rate, to remove the chloramine that is added to Edinburgh's water. If you have no chloramine to remove, the 480ml bottle will treat four times the amount of tap water, namely around 7500 gallons.

The water is then aerated strongly and heated to the ambient temperature of the room and stock tanks, which takes from three to six hours, depending on the incoming mains temperature.

Water changes are then effected by simply syphoning water from these reservoir tanks into the tanks in use. Drainage for waste water from tanks is in the water cupboard adjacent to the room.

fishroom



For a set up with over 1200 gallons (5400 Litres), this arrangement allows for 50% of water in all tanks to be changed each week by doing one or two changes per day (each change takes 45-60 minutes). In practice, the Malawi tanks get at least 50% of water changed each week, the Tanganyikan tanks a bit less.