Upgrading 2 tanks into 1

[Simund]

I currently have a fully stocked and established 15 Gal cube along with a cycled 13.5 Gal fluval. I am upgrading these two tanks and combining them into a 47 Gal tank. If I take the live rock and filter media from both of my current tanks, will this alone be enough to cycle the new tank instantly if I move fish and tank same day, or do I need more established live rock? About 25 lbs of rock between the tanks.

 

[Subsea]

I see this is your first post. Welcome to r2r.

With respect to nitrification bacteria, your new tank will be inoculated. Expect numerous mini cycles during the process. Consider starting a tank journal in members tank forum. to document the process

 

[edsbeaker]

I currently have a fully stocked and established 15 Gal cube along with a cycled 13.5 Gal fluval. I am upgrading these two tanks and combining them into a 47 Gal tank. If I take the live rock and filter media from both of my current tanks, will this alone be enough to cycle the new tank instantly if I move fish and tank same day, or do I need more established live rock? About 25 lbs of rock between the tanks.

If the combined bioload is the same as when the tanks were separate you will have enough filtering capacity in the 40 gallon. Just take your time adding more critters since the filtration needs to catch up to the bioload as that increases.

If your established tank has been running for awhile, you will probably have less risk of unleashing an ammonia spike if you use new sand instead of the old sand. Old sand tends to be filled with detritus and all kinds of disgusting things that will unleash ammonia if disturbed.

Have fun with the new tank and welcome!