Each HB had a physical filter (VEf = 10 L, clarifier with plastic mesh 0.4 mm hole). PVC pipe was used for water pipelines, the internal motion was carried out with a submersible pump (BOYU, ACQ-6000) and to each pond air was injected (53.5 L min_1, compressor BOYU ACQ-009) by silicone hose (Ø 4 mm) connected to four stone diffusers.