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Leachate sewage ponds at Phuket Integrated Waste Management (Phuket, Thailand) are typical hypereutrophic red-water ponds found at sewage treatment plants and piggery, feedlot and poultry waste ponds with mixed communities of anoxygenic purple photosynthetic bacteria (PPB) (Bacteriochlorophyll a) and Chlorella-type green algae (Chl a + b). In vivo integrating sphere spectrometer scans (Model AE PPB, Eopt = 386 ± 15 μmol quanta m−2 s−1, ETRmax = 316 ± 7.3 μmol e− g−1 BChl a s−1 but in a mixture of Chlorella and PPB only the oxygenic photosynthesis could be detected. In sewage pond samples, PAM rapid light curves in the presence and absence of DCMU allowed separate estimates of oxygen and anoxygenic photosynthesis to be made only if the Chl a content was very low (Chl a ≈ 0.26 μg mL−1; BChl a ≈ 1.4 μg mL−1). If substantial amounts of Chl a were present, fluorescence from PSII overwhelmed the signal from RC-2 of PPB, preventing the detection of anoxygenic photosynthesis. New PAM technology to measure Chl a and BChl a fluorescence separately is needed.

This study investigated using aquatic flowering plants (Canna generalis L., Typha angustifolia L., Echinodorus cordifolius L. and Cyperus involucratus [Rottb].) for nitrogenous waste removal from tropical aquaculture fishponds. Two plants which had higher removal efficiency (Canna generalis L. and Echinodorus cordifolius L.) were selected for further study in different light intensities and substrates. The effects of different light intensities were significantly different (P 0.05), but higher planting densities were counterproductive in terms of both water quality and fish survival. Flow rates of >100 % day−1 were needed for efficient nitrogenous waste removal. Red hybrid tilapia in the optimal setup (50 fish m−2, 12 plants m−2, 100 % water turnover per day) had weight gains of 629 %, a survival rate of 82.7 %, a feed conversion ratio of 0.72, and a specific growth rate of 4.7 % day−1 over a 6-week experimental period.