Tank Cycling

[DennisF]

I am going to be breaking down one of my 125G tanks in the next couple of weeks to move the 300 into the room. I plan on moving all of the fish and corals into the other 125G and leaving it running while I set up the 300. The 75G common fug/sump will be moved to under the 300 and the 125 re-connected to it as well as another 30G sump for the MSX250 skimmer. My question concerns my plan to connect the 300 to the fug/sump and keeping the 125G(with my fish and corals) connected to it also. I plan on about 2-3 inches of new sand in the 300, all of the rock will be cured rock from the existing 2 125's. What are your thoughts on the plan? Do you think I will experience a cycle on the new tank because of the new sand? The common sump/fug will mix the water from both tank. I am mainly worried about an ammonia spike. From what source I don't know since the live rock is all cured. Any input is appreciated.

 

[Wes]

id just keep a close eye on it and have water ready in case you need a water change, bet you will be ok since you have the 125 still hooked up and im assuming you will reuse all of the old water from the second 125. will be like a big water change and on ~500 gallons of system volume i bet the sand wont give you much trouble.

 

[DaveJ]

So long as the sand is dead to begin with and you are using existing LR that is coming straight out of tanks, you should be just fine. The only time you need to worry about cycling with sand is when you use existing sand.

I would suggest you go 2 inches though, anything more and you'll see a buildup of nitrates and detritus in the sand and vaccuming a tank that size is a chore.

You should be prepared for the normal diatoms etc however, adding dead sand will probably cause you to go through that, though it won't be nearly as bad as if you were cycling from scratch.

Try to use as much seasoned water as possible too... connecting the 300 with all fresh saltwater to an existing tank may stress corals out. The fish will probably be fine, but corals could get a bit of a shock.