Unfortunately, the petco here on the island of oahu doesn't carry it
In general, Petco carries crap for fish meds. When I lived in Alaska, I would buy most of the stuff off ebay just so I would have it on hand - just in case.
You may want to pick up the anti parasite meds you need AND something that fights gram negative bacteria like Furan 2 or Kannaplex, just in case you need it in the future. That way you will have it on hand in case you ever need it. Some diseases can kill in a few hours
In other news, how do people NOT do 100% water changes every now and then? The amount of crap...literally...in my 20G was just...EWWWW
I guess that happens when you got a bunch of these things running around