These are drinking water filters designed for RVs.
They are focused on removing things that negatively affect taste and chlorine, but they won’t remove things like calcium and magnesium which add to the total parts per million
They are similar to what @zparkie2 is talking about here
The ones I’ve seen look similar to this and contain a single carbon filter
Once again, it’s all for taste and not growing if it’s a filter like this although it’s still good for quick chlorine removal