I have taken tanks from my zip code to another and reused everything without deaths.
if you purchased such a bad algae problem I would keep fish in empty tank and put everything out to dry and setup what would be your main tank from scratch.
Pointless to inheret someone else's headaches when eventually you will have your own issues to deal with but if you want just keep the tank as is do water changes until nitrite and amonia are zero, if you truly have crabs and snails in the tank still alive then fish would survive as well.
Do you really want to fight hair algae and other issues from day one...
if you purchased such a bad algae problem I would keep fish in empty tank and put everything out to dry and setup what would be your main tank from scratch.
Pointless to inheret someone else's headaches when eventually you will have your own issues to deal with but if you want just keep the tank as is do water changes until nitrite and amonia are zero, if you truly have crabs and snails in the tank still alive then fish would survive as well.
Do you really want to fight hair algae and other issues from day one...