The abundance and diversity of the plankton community represents the health of the aquatic ecosystem, and plays an important role in the growth of cultured animals under aquaculture conditions. TWC and TWC + were effective bioremediators of eutrophic water, whilst a combination of TWC + B was effective in short term bioremediation and in promoting phytoplankton abundance in C. cainii physiology, weight gain or survival. TWC had no adverse effects on phytoplankton abundance or diversity, or C. After addition of TWC + B, there was a significant decrease in the concentrations of nitrate and total phosphate, and a higher abundance of phytoplankton was maintained than with other treatments. In the second experiment, concentrations of TAN, NO 2 -N, NO 3 -N and total phosphate were not significantly affected by TWC. The concentration of orthophosphate was reduced in aquaria with TWC +. In the first experiment, the concentration of TAN decreased more rapidly with Bio-Aid, whilst the maximum concentrations of NO 2 -N and NO 3 -N were reduced with the substrates. The second experiment studied the effects of TWC, a bacterial additive, and a combination (TWC + B) on concentrations of nitrogen and phosphorous, phytoplankton abundance and diversity in outdoor freshwater crayfish ( Cherax cainii, Austin and Ryan, Invertebr Syst 16:357–367, 2002) tanks. The first experiment studied the effects two substrates of different oil composition (TWC, TWC +), and a commercial bacterial additive (Bio-Aid) on concentrations of nitrogen and phosphorous in indoor aquaria. Two experiments were conducted to evaluate the efficacy of an oil-based substrate, The Water Cleanser™ (TWC). The results suggest that TWC can be used to improve juvenile marron production. In old ponds, there was a significant increase in juvenile marron final biomass of 26.3% with TWC, attributed to higher survival rate. There were no significant effects of TWC on phytoplankton or zooplankton abundance and diversity. Water quality and natural productivity in old and new ponds showed temporal fluctuations. The phytoplankton abundance, after 6 weeks and 18 weeks, and bacterial abundance after 6 weeks were significantly higher in old ponds. The initial concentrations of NO2-N, NO3-N after 18 weeks, and orthophosphate after 12 weeks, were significantly higher in old ponds. At the end of 7 months, TWC had no significant effects on the concentration of total ammonia nitrogen (TAN), nitrite nitrogen (NO2-N) and nitrate nitrogen (NO3-N), but reduced the concentration of orthophosphate. The farm had 21 ponds, categorised as: 10 new ponds (2 juvenile, 4 grow-out, and 4 brooder 5 with TWC, 5 without) and 11 old ponds (5 juvenile, 4 grow-out, and 2 brooder 5 with TWC, 6 without). The effects of a commercial substrate (The Water Cleanser™) (TWC¹), and pond age, on bacterial abundance, nutrient concentrations, natural productivity and marron production, were investigated on a commercial marron (Cherax cainii) farm.
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