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I personally think no fish should be used for cycling..
But as the damsel gets bigger it will get more aggressive. If you really want to keep him try stocking your tank with everything you planned on, then taking out the damsel for a week or so, and putting him back in so he has no established territory.
If you really like the fish like I do just start another tank and have a one fish only tank. You wouldn't be the first that did that I have a nice 24 with a blue devil.