How much ammonia is too much? The quick answer is: if a test kit
is able to measure it, you've got too much (i.e., it's in a high
enough concentrations to stress fish). Consider emergency action
(water changes and zeolite clay) to reduce the danger. (A more
detailed discussion of ammonia toxicity can be found later in
this section.) In aquaria-speak, the ``nitrogen cycle'' (more
precisely, the nitrification cycle) is the biological process
that converts ammonia into other, relatively harmless nitrogen
compounds. Fortunately, several species of bacteria do this
conversion for us. Some species convert ammonia (NH3) to nitrite
(N02-), while others convert nitrite to nitrate (NO3-). Thus,
cycling the tank refers to the process of establishing bacterial
colonies in the filter bed that convert ammonia -> nitrite ->
nitrate. The desired species of nitrifying bacteria are present
everywhere (e.g., in the air). Therefore, once you have an
ammonia source in your tank, it's only a matter of time before
the desired bacte