I totally agree with you ! Being a fish keeper, I like to know everything about my fishes. But like alot of people i made a big mistake ( ~3 months ago ). I currently have a 20g and a 5g tank. i made the mistake of buying 2 marble Walking catfishes for my 20g tank. The biggest mistake i could do ! THEY GROW OVER 1 FEET LONG !!!. now they are about 6 inches long each. Luckily i dont have many other fishes, Only small bottom feeders and 1 albinos claw frog. They are not Outgrowing my tank for now ( catfishes ), But soon will !
( Im not blaming the guy at the shop, 100 % My bad. But he could at least told me they grow that long , that fast

).
That just mean , Get informed people before buying something alive !
And for the substrate at wallmart, It is normal ! They replace the fishes frequently. The fishes will do fine without substrate. They just need to have the good water parameters and be fed everyday.
Amen to those walking cats! They're also quite aggressive toward one another, especially after pairing up. I didn't know that.
I think most people in the aquarium hobby start out as impulse buyers and overcrowders. Surprise whenever someone buys a Pangasius sp., channel catfish, gar, pacu or red-tail catfish. Most of the time it's just sad for the fish.
I remember growing up my step-dad had a 10 gallon tank stuffed with everything he could fit in there. A common plec, angels, bala sharks, cories, Chinese Algae Eaters, guppies, tetras and no heater. Surprisingly enough the tank survived a few years but it sputtered out and we never knew why. When I started keeping my own fish I tried my own versions of the overcrowded 10 gallon which kept failing and I got my first pair of convicts. It was all downhill after that...in a good way lol.
about the substrate, knife fish, dragon gobys, reed fish, spiny eels, and bichirs all require hiding places and if they dont have them they get stressed, in these tanks there was absoulutly no place for them to go, it was kind of sad.
Spiny eels would most certainly be stressed without substrate to hide in as they commonly bury themselves in it. The other species don't
need it. And hiding places would be nice but at a retailer where fish move quickly it is sort of unnecessary. Nice for the fish but it is not detrimental to their well-being. It helps the customer make an educated decision on their choice of fish.
maybe you should read it better, i said nothing about lack of substrate being disgusting, the discusting thing is they have fish with ick all over them no fins, and missing eyes.
Funny, you mentioned nothing about the fish having ich, no fins or missing eyes.
what i saw disgusted me, they had a single tank with a few african knife fish, two african butterfly fish, a few dragon gobies, and 3 pacus, with nothing in there except of a glass floor
Before getting my leo, I had a couple different books on how to care for them. Now I have 3 different books and they all contain slightly different information (temps, info on feeders, etc.). Of course, the gals in the pet store were no better, but if the research a person does before buying isn't complete there will still be problems.
I've kept herps on and off for several years and it's funny you should mention that differing information as I've noticed, just recently lurking on herp forums and looking up caresheets that one person's opinion on how to keep a species can completely differ from another's.
It's similar with fish keeping but not nearly as difficult. After a while you start to learn who's information is more accurate than the other's. Fish all come from very wet environments and it's a good idea to keep them that way ;-) . You can't mess up on a herp's temperature and humidity levels like you can find a pH range and hardness level that's simply reasonable enough for a fish to live in.
A minimal amount of research will be helpful when purchasing anything, so as to get an idea of how to keep it but I do believe all the details should be covered beforehand. The major difference with herps I notice is the lack of info on species that are not as common or popular.