These are some of the links I have used and found to be sources of reliable information about killifish.
This is the premier killifish club that has been around for years so if you are interested in killifish, it may be a good idea to join this one. With a membership you will get access to “The AKA Beginners Guide” which is about all you need to get started. Also be sure to check out the affiliate club section for local clubs.
Frans Vermeulen an expert and collector of South American killifish. This is a great reference source for South American killies.
This is Tim Addis’s site about African Killifish and is a great reference for those interested in them.