Sorry for your loss
Yeah the ammonia spike is from him passing...
To do a fishless cycle:
Go to an ace hardware or similar type store and get janitorial ammonia, it has no additives and is 10% ammonia so a little goes a long way.. dose to 2 or 4 ppm
(lower or higher based on weather you plan on lightly or heavily stocking) and keep it dosed that high, don't worry about water changes unless your ph crashes, after its eating through 2 ppm
in 24 hrs start checking nitrItes. Keep dosing with ammonia to 2 or 4 ppm
, once nitrItes are down to 0, wait 24 hrs for remaining ammonia to be eaten up and do a massive water change (like 95%) and after checking to make sure your nitrAtes are in the acceptable range and you're ready for fish
But be patient, the whole process can take weeks if you start without any seeded material.