The vinegar test can be done with any acid, the stronger, the more fizz. It's a test to see if the rock is a calcite (meaning formed with calcium carbonate) rock like limestone.
If you put a calcite rock into your tank it will slowly dissolve over the years. It's releasing calcium carbonate when it's dissolving, so it will act as a buffer, however it will make your tank have very hard water, which is probably a bad thing.
However, if you found them at the beach, they're probably not a calcite rock. If you found it in a place with a lot of sinkholes in the region (i.e. Kentucky) you're most likely to be in a karst topography, which means the bedrock, and most of the rock you find will be calcite.