Experiment 1 (E1)
The pond water was of good quality throughout the course of the experiment: Secchi clarity was
> 35 cm; pH cycling diurnally between low and highs of 6.3-6.5 and 6.8-8.8 respectively; and dis- solved oxygen cycling diurnally from > 7 mg L-1 at
15.00 h to minimum values of �3 mg L-1 L at
07.00-08.00 h. Concentrations of nitrite (< 0.015
mg L-1), total ammonia-N (< 0.25 mg L-1) and
phosphate (< 0.2 mg L-1) and hardness (< 50 mg
Ca equivalents L-1) were low. Apart from normal
diurnal variation, water temperature was fairly con-
stant throughout the experiment with minimums
and maximums typically in the range, respectively,
of 29-30 oC and 31-32 oC (Fig. 2).