My tap water has 5ppm nitrate and I keep mostly big fish, and they can muddy the waters quickly (metaphorically speaking), so never zero.
Probably you acquired a compromised guppy, poor little guy. I’ve purchased many fish online. Most come with an added $40 overnight UPS or FedEx fee. I like Imperial Tropicals in Florida and Live Fish Direct in Utah. But do check out local Facebook groups. I am not a FB person myself, but the owner of Imperial Tropicals told me to join his group because of my endless questions. From there (FB) I got into a pair of local groups & found some great prices on fish and tanks. Got two 125s, a 110, a 90 & a 75 all at ~25% of the retail value, same for three very nice canister filters. Many people get into and out of this hobby quickly for various reasons. You can also post in the local FB groups that you’re looking for a specific type of fish. Or ask someone who has the fish you want where she got it from.
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