the 25 has been running for 3 years and always has used tap for water changes, the 2.5 has been running for 3 or so months that water i used from the 25, the 30 is 2 weeks old almost but i used some already cycled water from a 3000 gallon system a buddy of mine has in the pet store he owns, i should clarify i use tap for water changes, and if its safe enough to drink its good enough for most fish, but if you have finicky fish i would use RO water :happy:
the filter purifies the water , takes out the hard stuff