Take him back in a baggie petsmart has 14 day gaurentee
YES!! Ask them for a little bit of gravel or a piece of filter medium or something else as well for not providing you with the necessary information to sustain the life of your pet!! I get free stuff all the time from my petco- they ARE informed and very diligent, luckily.
Here is a couple things that you can do to try to quicken the process a little bit, and tips to keep in mind- from my own personal experience.
If money isn't too tight there is water by carribsea called ready water, it has beneficial bacteria added, it's about 6 bucks for a 2.5g jug, just one of those with the rest preferably distilled water, walmart brand 88 cents a gallon.
Using filter media that supports bb growth (nitrite and nitrate inhibiting) will help you get through the nite process easier with slightly less chances of stalls/ crashes.
If using tap water I strongly recommend using a water conditioner to remove chlors and heavy metals at the very least- there's some concentrates that are pretty cheap, but since this is your first cycle I would suggest a product like seachem prime, nutrafin aqua plus or amquel+.
Your first readings that come in will be ammonia, try to keep those BELOW .25 by doing water changes- don't use ammolock until your tank is stable- it can stall your process. Instead try using something like seachem stability, nutrafin cycle, API StartZyme+ or StressZyme- something to encourage beneficial bacteria to grow rather than chemically "freeze" the ammonia.
Once ammo drops your nitrItes will spike, keep up with water changes to keep those in check- special blend nite out 2 used at half dose can help out if it spikes too high. Try to stay below .25, again
Next is the dreaded nitrAte spike, this one can bite you in the butt if you get ahead of yourself, I stalled in phosphates because vanity drove me to try API Algaefix- use me as your example and please don't do it, lol, just keep doing water changes and try not to disturb your substrate i.e. gravel, sand, rocks etc or decor, just use a turkey baster to remove excess food or fishy poop. Beneficial bacteria (bb) is establishing itself. Try to keep trAtes below 4.
Things should start to stabilize, ammonia, nitrIte, and nitrAte levels should all drop to 0. Keep that reading steady for a week and it's time to start thinking about who you want in your tank
I was describing the fish-in cycling that I use for freshwater. Fishless cycling I have only done with saltwater, but I know it's posted everywhere so someone can tell you that method. I know it starts with using PURE ammonia and adding enough to reach 5ppm
Here's some of the fish I have used for fish-in cycling. Giant danios, pleco, goldfish, betta, gourami, cherry and ghost shrimp.... If you decide to use goldfish or pleco remember you will need a very large tank or eventually rehome them.
Good luck!! Keep us posted on your progress!!