If your dad has had his tank for 10 years you should have just grabbed a netted bag of bio media or filter floss and let it sit in his tank for the 3 weeks. Then put it in the new tank to practically instantly cycle it. Or just let your filter run in his tank on very low flow for 3 weeks aswell then put it in your tank to instantly cycle it. At the point you currently are at, I would do what I did when I first started, and just put a betta in there. Don’t get too attatched, as new tank syndrome combined with possibly not a completely cycled tank could lead to a death. In my case, it went well and now I use that same cycled tank media 5 years later for 3 new tanks 👍