So guys, how much of a cycle do you think I will have when I switch over the 125 to the 350? I will have a new sump, I will have some new sand, but also all that was in the 125.
Well, it's about a 36% change, if you use ALL from the 125. I would agree with dmjordan.
If you keep all changes within that % range.
What a great moment, though! If you have kept these fish for 4 years, I'm sure they are healthy and ready for the move.
Depends on the health of your sand bed.
If you have a healthy sand bed it will be clean and you'll not have any cycle (unless you order LS from online and shipping kills some of it). If your sand bed is dirty you could have a significant cycle by stirring it up.