With the 145 lbs of rock you already have, the additional rock should not really be much of a problem unless you have animals in the tank. The old rock should be able to process any die off the new rock might have. I would even be willing to bet you only see a marginal increase in NO2
depending on what condition the rock arrives in. From what others have passed along about LR
.com, I don't even think water changes will be needed but I would still be prepared.
If you do need to do water changes, about 20-25% depending on the NH3
, when using uncured LR
to cycle the tank, the amount of nutient is usually quite high and water changes will not really prolong the cycle that you'd notice. It's typically in new systems that are using well cured or no LR
that it can prolong things due to insufficient nutrient/bacteria being available in the first place even when adding a fuel source.