Advice please

[Yateley Al]

Good evening, my name is Al and I live 30 miles west of London, I have a Fluval 252 tank that currently has six discus and a bunch of smaller tropical fish that we call the clean up crew, we’d love to convert to marine but we need advice on how to do this

 

[Gumbies R Us]

https://www.reef2reef.com/threads/can-i-just-add-salt-to-my-freshwater-tank.699776/ This should provide you with some good information!