"chris nuttall" wrote in message
om...
what is 'old tank syndrome'?

chris

Basically, everything organic (uneaten food, fish waste, dead plant
matter etc) slowly gets broken down by bacteria releasing ammonia, and
acidifying the water (by first reducing your buffer and then reducing
your pH). Under normal conditions, this extra ammonia is consumed by
nitrifying bacteria and the acidifying effect is absorbed by your water's
buffer (also known as the karbonate hardness or kH). The buffer is
replenished by routine water changes.

In tanks which have been running a long time and/or haven't been properly
maintained, this dissolving organic matter (detritus or mulm) accumulates
in the gravel and its effects begin overtaking the aquarium system's
ability to cope with them. In hard-water tanks, this manifests itself as
very high and persistent nitrates (NO3). In all other tanks, OTS
manifests itself by extremely and persistently low pH.

You can detect the onset of OTS in most tanks by measuring to see if
there is a significant difference between your source water kH and your
tank water kH (usually measured in degrees or dkH, ie: under 2dkH =
danger, under 4dkH = caution - dependant on application). hth

http://www.2cah.com/netmax/basics/water/water.shtml#ots

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