Who Do You Trust?

Ignore YouTube. Anyone who has no knowledge whatsoever can make a video and sound like an expert. There are some horrors on there.

Facebook, the same.

Websites can be written by anyone as well, regardless of how much they actually know.



The best places to look are websites written by experts.
For corydoras, look at Corydoras World. The chap who runs that is the world's leading expert on cories.
Catfish, including cories - planetcatfish.
Loaches - loaches online.

For general fish, the profiles on here were written by a fish expert, although they don't give as much info as other sites, and there many fish in the profiles.

I concur with all of the above (and Seriously Fish has the benefit of being kept up-to-date) - plus the names of those well-regarded in the field (eg INJAF was written by such). Peer-reviewed literature, especially systematic reviews of primary studies, are a great source - but unfortunately few/none of these exist for fishkeeping, from what I can gather.