established system water to seed a new tank

[fugu]

is it advisable to use some water from an established tank to seed a new tank?. my 40 gallon is now becoming a QT tank. there is an undulated trigger in there only. he is being moved to a 75 gallon, which is currently cycling. can i use some of the water from the old tank and replace it with the water from the cycling tank in place of performing a water change on the 40 gallon? the 75 gallon has been running for ten days so the water should be ok to use for a water change for the smaller tank. any ideas?
thanks in advance

 

[slk3599]

Switching water around will not help the tank cycle any faster. Use some of the substrate of the old tank to seen the new. The bacteria you need is in the substrate.