Thats unfortunate you lost your gar. As far as their size and what they can and cannot eat for lives you be surprised at what they can muster down. I know nothing about eels so i cannot state if this is a good or bad combo. Perhaps you could section off a portion of your tank until they are of a size that the eel would not consider. Rich I also had a large common pleco i got rid of when i added my gar, better not to take any chances. I will admit they are much more amusing and active when kept in pairs. I hope all works out well for your remaining gar.