I keep a Gymnothorax Funebris, is this the green species you are enquiring about?
He/she is 5ft long (give or take a few inches) and as thick as a man's thigh. It is in fact the second one that I have owned, the first one escaped during maintenance and attempted to attack my wife!!! so it had to go unfortunately.
As for care, you really do need the biggest, baddest marine system that your resources will allow. To keep one, you need to understand that Gymnothax Funebris resides at the top of the food chain. They have very very few natural predators. I understand that some keepers have managed to raise them with tank mates, but I can assure you that is the exception, rather than the rule. The G. Funebris will devour its so called "buddies" eventually, for sure.
I have attempted to raise them with very large Groupers, Snappers, Volitans, Triggers, and my beloved Sphyraena (Barracuda) and they all disappeared eventually.
I had a 13inch Clown trigger, a fish that liked to dominate the system at all times. The trigger would nip at the morays fins, then one night, when the lights went out, and the trigger was resting, the angel of death came calling, and the trigger was destroyed by the moray. The only living creatures that are safe with them, are the cleaner shrimps. However there may be one exception that I know of, I am trying to locate an adult "Enchelynassa Canina" (Viper moray) There might just be an outside chance that the G. Funebris will accept it.
The G. Funebris will move and hunt during daylight hours, as well as night, so you will see plenty of the moray. They truly are magnificent creatures to observe, and I can promise you, that there are very few sights in this hobby that can match their awesome power when in a feeding frenzy.
I feed mine live squid. mackerel, and as treat, octopus.
Here is mine.... peace.
