if you moved, you may have "New" water(from a new source)...i just moved 3 months ago, and i couldent get my ates below 15...turns out my RO water is 20...so check to see if your water has nitrates in it.
also 15 isnt bad, you moved the sand bed and rockwork around, so you have probably sturred up dead stuff, or caused some minor dieoff when moving the rocks around...just make sure you drip the fish/inverts to get them use to that "NEW" water.
do a 3~4 20% changes over the next 2 weeks