this fish can get little over 18 inches it is predator in every since of the word they donot like each other they will fight no matter how you set your tank up .and if you get them small and raise them togeather put several in one tank does not matter they do get a long with most mid sizes to big fish who do not think its food vary smart fish can be agressive will eat fish, clams, squid,and bloodworms weird but they do. they are also harmophdites well in this species they lay eggs guard them they will go into a crazy frency like eat there on eggs bite there tales they will be nice in a med size Aquarium of 50gallons I kept mine in 65 and 75 gallonS SAME WATER PERAMETERS as most saltwater fish I always like to get them around 7-8,inches and grow them up I have gotten big eels 12-16 inches just watch and moniter the fish it is fun to see what it does next the fish is really smart and fast the temp should be 78-82. they like hiding place to lay low but it will be all over the tank but don,t forget all fish are different I kept them for over 15 years all arrangements .not good for a reef tank fish only.