Welcome to AA! Here's some stuff that might help you:
One thing to keep in mind is that fish can tolerate a much wider range of water conditions that you might think, provided you let them acclimate to it. Using chemical products like pHup or things like baking soda is going to make it very hard to keep the pH stable, and fluctuating water conditions like that will in the end be more stressful on the fish than a pH a little out of their range. If your pH is 6.2, it's not so bad as you would think. Plenty of tropical fish have pH ranges that extend down to 6.0 and lower, so as long as you do a little research and don't mind settling for only low-pH fish, you should have plenty of options.
Really, the only real negative side effect of an innapropriate pH will be that the fish are less likely to reproduce, but unless you are actively seeking this, it shouldn't be too big of a deal. One thing to keep in mind is that the average range for stream water pH is about 5.5 to 7.5, and a lot of freshwater tropical fish will have lived in streams in the wild.
If you are still concerned over your fish and want to raise the pH, you do have some options left for doing so that don't resort to chemicals. Make sure your water is well-oxygenated (get a bubble wall or an airstone if neessary). To much CO2 in your tank will lower your pH and your fish will love all the oxygen in the water. Also keep up with cleaning a little more than you otherwise might, since decomposing matter in the tank will release carbonic acid into the water, which acidifies it. You can also add coral (as suggested above) or limestone to your tank, either as decorations, or in the filter, though the former will likely be a lot simpler. Some people even use a coral-based substrate. I believe this works by leeching calcium into the water, which raises the pH.
Something to also read up on is buffering your water. The more buffered your water is, the less drastic any pH fluctuations will be. See what looking around the internet for water chemistry and kH and gH will get you. I personally don't have a lot of knowledge in this area, so I can't really help you out there, though someone else here might have some suggestion regarding it.
I hope this helps, and good luck with your fish!