waterdrop
Enthusiastic "Re-Beginner"
Yes, its generally a good approach to separate ones thinking about mineral content and pH in the tank during cycling from mineral content and pH in the tank after cycling is over and the tank is running normally.
The tap water gives some idea of the baselines the tank might be near once cycling is over but is not entirely the same as a running tank, so its good to be planning to watch the pH and mineral content for a period after you get fish (assuming one understands what its likely to be well enough to have made the stocking choices) which should hopefully give a more true idea of what it will be like for years to come.
What model of eheim filter is it? Most of the larger eheim external cannister filters run several trays of media and often one of those trays contains a gravel-like material called ehfi substrat (or a larger, rounder ehfi substrat pro) which is really a sintered glass ceramic gravel. What you could do in this case is buy a box of fresh ehfi substrat for the donor and then together you just be careful to not take more than 1/3 the volume of this substance in the mature filter and replace it with an equal amount of the fresh media. Your friend should never even see a blip in the performance of the filter.
~~waterdrop~~
The tap water gives some idea of the baselines the tank might be near once cycling is over but is not entirely the same as a running tank, so its good to be planning to watch the pH and mineral content for a period after you get fish (assuming one understands what its likely to be well enough to have made the stocking choices) which should hopefully give a more true idea of what it will be like for years to come.
What model of eheim filter is it? Most of the larger eheim external cannister filters run several trays of media and often one of those trays contains a gravel-like material called ehfi substrat (or a larger, rounder ehfi substrat pro) which is really a sintered glass ceramic gravel. What you could do in this case is buy a box of fresh ehfi substrat for the donor and then together you just be careful to not take more than 1/3 the volume of this substance in the mature filter and replace it with an equal amount of the fresh media. Your friend should never even see a blip in the performance of the filter.
~~waterdrop~~