Recirculating aquaculture system (RAS) are frequently used in the production of ornamental fish in captivity, where acidification occurs due to the nitrification process. In this study it was evaluated the production of juvenile clownfish Amphiprion percula in RAS, at pH 6.5 and 8.0 in brackish water (BW - salinity 11‰) and sea water (SW - salinity 33‰). When fish was kept in BW, there was a negative effect of acidification on survival and growth. Nevertheless, production of clownfish in BW at pH 8.0 results in color improvement.
Recirculating aquaculture system (RAS) is a suitable production system, when located away from the coast, the use of low salinity water can be an economical option. However, water acidification is commonly observed in RAS, due to the nitrification process. In this study we evaluated the production of juvenile orange clownfish Amphiprion percula in RAS, while exposed to different pH (6.5 and 8.0) in brackish water (BW – salinity 11‰) and seawater (SW – salinity 30‰) for 45 days. The experiment was run with triplicate tanks and stocking density was equal to 20 fish per tank. Our results showed there is no harm to rear clownfish at pH 6.5 in SW. On the other side, production was compromised when were reared in BW at low pH (6.5). However, our results confirmed that it is possible to produce orange clownfish in BW, as long as the pH is kept at 8.0 (Figure 1). It is noteworthy that 38% of the clownfish reared in BW, independently of the pH, developed a partial melanism typical of the onyx variety, which is more valuable than the normal fish coloration in the ornamental fish market (Table 1). In conclusion, the combined effects of low pH and low salinity compromised growth and survival of juvenile orange clownfish, but production in BW leads to color benefits.