I have just tested my fish tank today for the first time and the ph level is 5.0, Im new to tropical fish and dont know what to do next. I have had my tank running for 2 years with coldwater fish, 4 danios, 2 neon tetras still left. Put a heater in to convert to tropical 2 weeks ago and have added 1 male siamese fighter. 3 platys, 1 dwarf gourami and 3 gold barbs. All fish are lively and seem very well but cant understand why my ph is so low. My ph in the tap water is 6.5. Can anyone help me please on what to do.