what is the worst advice you've ever had?

[oscar fish lover2000]

Hi guys, what is some of the worst advice you've ever had about keeping fish or other aquatic animals?
my worst advice was a long time ago when i was about 7 years old, i was told that fish would grow to the size of your tank,
well my mum bought me a 20 gallon tank and i had 10 goldfish in it! in 1 year they were all dead except for 3!

 

[spankymaz]

On my first tank I was told the same thing from my lfs. So I ended up with 3 oscars in a 10 gallon.

 

[coryjames]

Was told I could add an oscar after my new setup had the filter running for 24 hours. No cycle needed!!!

They forgot to mention that if I added them within 24, that I would be doing 50% water changes once or twice a day for a month.

Thank you LFS