Boiling the water will decrease the amount of dissolved oxygen in the water. Cooler water has more, warmer water has less, and needs to "breathe" a while (not sure how long) for the natural gas exchange at the surface to replenish it. Can you make water changes with same-temperature (or slightly colder) water without boiling it? Add a de-chlorinator just in case, and everything they said about the surface agitation etc. Seachem's Prime is good b/c it also detoxifies ammonia in cycling tanks.