Lungfish
African Lungfish
There are 4 different species of African lungfish however the most common species to be found in the aquarium trade is
Protopterus annectens-Most common
Protopterus aethiopicus
Protopterus amphibius
Protopterus dolloi

Protopterus annectens
African lungfishes are easy to keep if you can dedicate a large aquarium to specimens since they accept a broad range of water values. They should preferable be kept in neutral to slightly acidic water.They eat anything that is offered to them including dry food. (You might have to train them before they accept dry food.) If a food source is too large to fit in their mouth they eat pieces out of it, this includes other larger living fishes. So don't assume that a fish is safe with your African lungfish just because it is too big to fit in its mouth.

South American Lungfish-Lepidosiren paradoxa.
The South American lungfish grows to be 1.2 m / 4 feet. South American lungfish can be kept in aquarium in the same way as other lungfishes.
They require a large aquarium which shouldn't house any other fishes due to their predatory and aggressive nature. The water should be neutral to slightly acidic. They accept any meaty food and you might be able to get them to accept dry food. Be sure to feed a diverse diet containing fish, crayfish, shrimp, and earth worms
There are no known successful breeding of South American lungfish in aquarium. They spawn during the rainy season and the male builds a nest in which the eggs are deposited. The male then guard the eggs and the young against other predators, egg eaters etc. The fry spend their first 6-8 weeks hanging from vegetation using adhesive glands. These glands are not present in older fishes.

Australian Lungfish-Neoceratodus forsteri
They have very small eyes and a long thick body which is covered in large scales. They are usually olive-green to brown with dark spots on the sides. The species is CITES protected but there are licensed breeders from which they can be bought. They grow upto 5ft/1.5m and weigh over 40kg. The Australian lungfish has unlike other lungfish only one lung.
Australian lungfish should when kept in aquarium be kept alone in a large aquarium with a neutral to slightly acidic water. They will eat anything meaty and their natural diet consists of frogs, tadpoles, small fishes, snails, shrimp and also vegetable parts. They detect prey by using their sense of smell and detecting electrical impulses.There are no reports of successful breedings in aquariums. They spawn during the night and it takes the fry 3 weeks to hatch. The fry grows slowly.
There also exist a few albino specimens of this fish. Those are however very rare and extremely expensive.