RTR said:Not cleaning the gravel may be a big mistake - gravel is an excellent reservoir for nitrates in old mulm.
Sorry, I just meant initially. If he added the mulm from the established tank to the new one to give the bacteria a day to establish in the new tank, then back to cleaning.
Try using filter media and/or squeezings from the old tank instead of gravel. There are more nitrifiers in the filter media than gravel, gravel houses mostly heterotrophs (the guys that break down detritus into mulm)