IAL isn't necessary
whatsoever if you just keep up with the recommended weekly water changes depending on the size of your tanks.
Bottled fish water is a complete ripoff. It's there to trick the parents & children who don't have time or are just too lazy to do the proper research on how to "condition" water.
For the price this "bottled fish water" sells for you might as well buy a new fish every 2 weeks.
A bottle of Prime conditioner to treat your tap water is far less expensive & practical if finances are an issue.