It does not matter. Use your tapwater. Rain water is unnecessary and quite tedious. Rain water is fine for use but in the long run, it is unnecessary. It doesn't kill bacteria unless your source is polluted.Drew'n'Kylene;3135362; said:Sorry its 55g and its for an oscar for the next year. Like i said it has cycled but the ph level is rather high. And i cant test for anything else coz the weathers been hectic and lfs have run out of Master test kits. I just wanna know if rain water will eff with my bacteria????