ok I feel dumb but what ph do guppies like

That pH is fine for guppies. The main thing is how different is it from the fish store's pH. I try to do a very slow 2 hour acclimation for new fish by slowly reaplcing the water in the bag with bits of water fromt he tank. This way the fish can easily get used to a pH and temp change.

That being saod many guppies these days seem to come from weak strains and don't survive all that well.

Johnny,
One way to acclimate them to your water is to do a SW trick. If you place some new ones in the water, you want to slowly add the water to your bag, like a cup or 2. This will help get your fish used to your tank water over a period of time instead of being tossed directly into it. I do it for all my fish, Fresh and Salt. For salt, it allows them to get used to the salinity in your tank. For my fresh, I use it for PH.

jim

did your gf buy those guppies for you?what kind were they males or females

Just a shot in the dark, but I'd say your tank wasn't cycled when the fish went in. The majority of cycle aids just don't work. Ammonia and nitrite are actually much more deadly to your fish than nitrates. A nitrate level of 20ppm should not be harmful to your fish btw, but at that level you should probably do a water change anyway. Not sure what sort of nitrate test they did, but on my chart the second level is 5ppm. I would say your single guppy is safe in the tank, but you should do water changes daily for the first 4 weeks or so. After about 6 weeks with the one guppy have the water tested again. If possible do it at 2 LFS that will test for ammonia, nitrite, and nitrates for you. If you show zero ammonia and nitrites then you can add another fish. Wait about 4 weeks more and test again. If still zero add two more guppys to get you back to the 4 fish. As previously asked do you have male or female guppys? I'm thinking a group of females in that small a tank would be ok. A group of males may get irritated with each other. Whatever you do if you do have mixed sexes go with 1 male and 3 females. The other way around and the males would chase the female to death.

Second tank = Instant cycle

You have another FW tank that is stable?

Take some of the filter "squeezings" from that tank and add to the filter of the new tank. Your old tank won't miss it, the new tank will instantly have the bacteria it needs.

You can do that daily until your tests say all is well in the new tank.

If the old tank has a cartridge, take some of the old tank water, swish the cartrdge in it to get muck off it, then pour that into the new filter housing, or just into the tank near the filter inlet. That way you are not risking contaminating the old tank with possible disease from the new tank, if the fish caught anything while so stressed.