Tell us about yourself!
Oh it's GOT harmonics, i don't have to build it for that, it's a square wave, odd harmonics everywhere. You fix it by using a lowpass filter, or better use a band pass filter. Basically since this is a crystal and you're not using any tuning mechanism, so it's a single frequency, you just want to pass that single frequency plus any intended deviation (up to maybe 6 kHz) and that's it. If you can't get that specific you want to at least block the harmonics, and subharmonics if there are any.
mouser.com or amazon should get you a whole bag of the suckers for 5 bucks