... cantherefore only occur in acid fresh water.There is a relationship between the CH and the general hardness: the closer the CHvalue comes to the GH value, the more bal-anced the water. If the ... is essentially the rear part of the body, particularly the caudal fin,which serves to propel the fish, while the other finsplay a stabilizing and steer-ing role. Of course, the more hydrodynamic ... hobbyists as there are typesof fish: the semiprofessional, the "small"and the "modest" collector, the specialist.There are the fanatics, who spend everyminute of their time...