I do not think that the stores you mention keep their fish humanely...but...the tank you see is part of a network of tanks and even larger tanks behind the walls. A bank of ten 20gallon tanks actually has 500 gallons of water all told (two 150 gallon tanks sit on the floor under the tanks you see), so they really have much more water than it seems.
What size tank do you keep these fish in? It looks like, from you pictures, the tank is not on a stand, but is sitting sideways on something? Be careful it doesn't warp and crack the glass. It really needs support across the entire bottom.
I agree with your wikipedia thing, but honestly if you stop and listen to these people, you can learn stuff. I'm not saying you HAVE to be their slaves and do exactly as they say, but I'm just saying they're giving good advise.
ok, those knife fish reach an adult length of over a foot long, the goldfish you have can reach a foot long in a year.
honestly, if you can't see that the pet stores are only interested in selling you as many fish as they can, there is no help for you.
think about it...if you listen to us, you buy less fish, less medicines (your fish will be healthier), less fish food. If you listen to them, you will have more fish die, you will buy more fish, constantly be buying fish medicines, fish food etc.
once you have a better grasp of what you are doing you can overstock a little by having a water test kit ( not just strips, a real deal kit), knowing the signs of stress (your goldfish aren't "napping", they cant get enough oxygen!), stocking live plants (these help your water if you know how to care for them) and in general not having your head up your ass.
Ryan, your fish may be 'Surviving' but as orangecones stated, theres a lot more to it than just keeping them alive.
The 2 goldfish to 30gl is just a guidline to the suitable size tank that goldfish need. You may have kept your alive in a 4gl but are they happy? your aquarium may be lacking in oxygen and toxins from your goldfish waste (and they produce large amounts of waste) will build up in your tank quickly.
There are people on this forum who have been here for a long time and keeping fish for many years now. Our experience is used on this forum to help other people, and that is one of the purposes of a forum.
if you really want to keep 2 and then re-home all of your other fish. Backlog of a 30-gallon tank only 2 goldfish, but the times of refreshing may successfully manage two goldfish in 30 gallons, so it may be weeks, water testing and changes.