EXPERTS How do you distinguish between the 4 different species of Jewel cichlid (Hemichromis bimaculatus)?

I found this page for you, it was alot easier than trying to explain it :)

It's impossible to distinguish if you are getting pet store stock because in Jewels they are probably hybred mutts. It is relatively easy to differenciate these fish if you get true pure stock. A lot of the older general aquarium books show Cristatus and say it's Bimaculatus so be careful. Get a new aquarium book that specializes in West African and it should be correct. Join a local cichlid club or get them from an importer. West African imports are starting to increase a lot over the last 2 years. I don't trust most of the importers in this area of Africa though the fish are wild so you can look at them closely and make sure you separate them out to make sure you are only keeping true cristatus or lifalili or whichever one's you request with themselves. Breeding Hemichromis is easy so once you have a true group you can help get rid of the hybreds and distribute true fish to friends. Beware of the 5 spot they are just vicious though the Bimaculatus, Cristatus and Lifalili breed easily and in at least a 55 gallon I've never had a problem with them being overly aggressive. Make a flat rock cave and they'll keep everyone away from that corner though they've only defended a 2' area for me. It seems like I've been luckier than others though I've found them to not be overly aggressive. If you want to breed the 5 spot you'll need a much larger aquarium and I haven't done this successfully though your question has peaked my interest. Maybe I'll get some and put them at least a six footer. I don't know the Paynei so I have no comments about it. I do have more Lifalili than I know what to do with and personally I find this to be the most attractive of the Jewels.

Lifalili Jewel Cichlid

When fish are classified and named by the researchers who do that sort of thing, they count the rays in the fins and rows of scales on the body to separate closely related species of a genus. If all those match, then you just have color variations of a species and not actual different species.

You might try googling each fish's name with "description" added to the search. It may bring up the details on fin rays and scale rows that you are looking for.