What size tank? Ya more than likely have Gymnothorax tile, as toddnbecka pointed out. The species can easily reach 2' or a bit longer. It will need brackish water for long term care.
The two other species of freshwater moray eel occassionally offered in the trade are Gymnothorax polyuranodon and Echidna rhodochilus (a.k.a. pink-lipped or white cheek moray). The white cheek moray stays 'bout a foot and eats mainly crustaceans and mollusks in the wild, but is purty opportunistic and will take small fish and can be trained to eat pellets or sticks with a little work. It will need brackish also.
G. polyuranodon can hit 4'. Contrary to popular belief that all morays need to be in saltwater as adults, studies throughout Oceania are starting to support a catadromous life cycle for this species (Ebner, Brendan Craig, et al. "Is the elusive Gymnothorax polyuranodon really a freshwater moray?." Journal of Fish Biology 79.1 (2011): 70-79.) Other articles are available from Fiji, the Phillipines, New Guinea, the Solomon Islands and northern Australia, I'll hafta do some more diggin' to find 'em as I wasn't able to find them quickly and I know this will likely stir somebody up. Anyways, it's the most likely to do alright in FW but will get large and need a larger tank.
As far as your gar, do ya have the true longnose or needlenose gar Lepisosteus osseus or do ya have the Asian Xenentodon cancila? The former can get 4' or 5' long, the latter tops out around 18". Both are FW fish, so eventually they'll need a separate tank from your eel.
WYite
