Biofilters are crucial and costly components in marine recirculating aquaculture systems. However, not much is known about the settlement of nitrifying organisms and developing nitrification rates during the start-up phases of these reactors. The nitrifying microorganisms in moving bed biofilters of two marine recirculation aquaculture systems identical in construction were monitored for 388 and 477 days by PCR based methods, accompanied by laboratory nitrifying activity tests. Ammonia and nitrite were added to the recirculating aquaculture system 1, while system 2 was spiked with fish feed. On day 88, system 1 was stocked with turbot (at 17 °C) and on day 126 system 2 was stocked with sea bass cultivated at 22 °C. The potential nitrification rates corresponded well to the conditions in the operating systems, and in both systems slowly developing nitrite oxidation rates led to high nitrite peaks. However, after 218 (biofilter 1) and 286 (biofilter 2) days, potential rates of nitrite oxidizing bacteria outreached those of ammonia oxidizing bacteria.

The present study was performed to examine acute toxicity of two water-borne metals (Hg and Cd) by static bioassays. Fingerlings Percocypris pingi (P. pingi) were exposed to a range of concentrations of heavy metals and the mortality rate were investigated after 24, 48, 72 and 96h. The median lethal concentration (LC50) was determined with Probit analysis. The LC50 values of mercury chloride for the P. pingi at 24, 48, 72 and 96h were 0.441, 0.347, 0.327 and 0.327 mg/L, respectively. But the LC50 values of cadmium chloride at 24, 48, 72 and 96h were 2.551, 2.341, 1.207 and 0.081mg/L, respectively. The toxicity ranking of the two heavy metals was Hg>Cd. The safe concentration of Hg and Cd were 0.0327 and 0.0081mg/L, respectively.

In the present review, we have described aspects of the color of marine shrimp of importance in aquaculture (mainly Penaeus japonicus, Litopenaeus vannamei and Penaeus monodon) and in the world. It is generally described some ecological aspects and some factors that affect the color of the shrimp. It describes in a general way, ecological aspects and some factors that affect the color of the shrimp, as well as, specific aspects like the color change, the importance of the pigments in the color and the effect of the cooking and storage processes on the color of the shrimp. As well as some strategies that have been used to improve the color during the last decades are discussed. As well as the ability to select genetic lines of color shrimp.