I cannot believe it is just newer members -- because where do the newer members get their myths in the first place?
Its not the newer members. I'm pretty sure most myths come from clerks and owners of LFS' who don't know wtf they're talking about. After working in the pet trade for a while I've found that this is where most myths get started. From major morons who don't know what they're selling, but do anyways. Then the customers that are told this info pass it on to others.
I once had a guy call me up and tell me he had just started a new tank and all his fish we're dying. He claimed he had called 3 LFS' and got 3 different answers to his questions. I asked him if he called the store where he purchased his fish and he said no (now right here is a good clue that this guy is a certified dimwit).
He proceeded to tell me the responses he had gotten from those stores. They were all wrong. One place even convinced him that it was his 2 inch plecostemus that killed his all his other 4-5 inch fish. I asked him some basic questions and found out that he overstocked his 10 gallon (the usual tank choice for idiots who want tons of fish, but don't want to do any work or read, or basically listen to any info on keeping fish). I explained to him the nitrogen cycle, and what the problem was inside his tank.
You'd better beleive this guy didn't want listen. He angrily shouted that he has gotten 4 different answers and he was sure that it was the plecostemus. Then he had the nerve to ask "why should I beleive you." To which I replied, "because I know what I'm talking about and those other people don't. If you want to listen to them then go ahead and watch your fish die and wonder what the problem is. You called here and asked for my help. If you don't want it then don't call." I hung up and never heard from the moron again.
Another time I had this jerk come in and tell me the fish in his 75 gallon tank had ich and they were all dying. He told me he dumped a whole bottle of medication in but nothing happened. I told him first, you never overdose your fish, second you have to take the carbon out, third his tank was way overstocked. Then I found out he had NEVER heard of water changes. I told him all about water changes, and also salt dips and other ways to get rid of ich. I told him good water quality was the best way to insure that his fish never got sick. For 40 minutes I argued with him as he insisted that there must be some magical bottle that you pour in the tank and you never have to do any work other than twisting the cap off. I couldn't convince him and he ended up stealing some quick dip test strips (I doubt that saved any of fish).
I've also had people insist that the one inch per gallon rule was true and therefore they should be able to put a ten inch oscar in a 10 gallon tank and that I must not know what I'm talking about when I tell them why their oscar died in their stupid little tank.
But the problem didn't stop there. Countless people have insisted that I was lying to them, or trying to sell them something when I told them how to be successful in keeping fish. I've even had other customers butt into my conversations and tell false information to the people I was trying to help.
Most fish myths arise from the same ignorance that created the "pit bulls have locking jaws." One idiot (or sleazy pet store owner), who didn't know anything about the animal they were selling, mixed up information and passed it on as fact. Then the consumer culture morons who buy but don't think passed this on to others. So please people, if you ever see someone passing on false information, punch them please.
Disclaimer: When I call people names, it does not apply to anyone on this board, for being on this board means that you have taken it upon yourself to learn more about your interests and therefore are not an ignorant fisj keeper.