Originally Posted by bskerrichard27
In my 55 I wanna replace the substrate I have about 100 lbs rock in dt and 15lbs in Sump what's the best way to go about this without causing a cycle tanks a year old
Were it me, I'd replace 25% of the substrate, then test parameters frequently. If all goes well, a week later, I'd replace another 25%, etc..
If switching out 25% of the substrate touched off a mini-cycle, I'd wait until two weeks after the cycle reestablished itself, and then reduce the amount of substrate being changed out at any one time.
At 25% I would imagine that any recycling you do get will be relatively small, short-lived, and easy to manage.