one to many fish in tank

Question

my tank   i have a 175gal freshwater tank,the  water conditioner, temperature,PH,is all right. i have a two sided bio filter i change it once every tow weeks. fish food is correct. i have about 30 small fish in the tank now.they are all the same size as a guppie fish.... but when i added new fish two days later some started to swim in a tilt. not sideways just a tilt. im going to attach a photo with this. do you know what is going on with them?

Answer
Susie,
Did you quarantine the new fish in your hospital tank for at least two weeks before adding them to the main tank? If not, the new fish could have been ill and now have given their problems to the other fish. It is very important that you never add new fish until you know they are free of illness and/or other problems. Since the only thing we know now is that they are swimming at a tilt, really is not much you can do yet. We never like to medicate our fish until we know exactly what the problem is. Since I do not know what type of fish you have, it is hard to tell you what could be going on. Some fish have problems that other fish don't. In order for me to help you better, please let me know what types of fish you have in the tank.