one question though
do you know if it is normal for him the breathe rapidly
That would depend much on what you think to be breathing so rapidly for eels can give you the idea that they seem at times doing so but in which is possibly normal as well. For if all its activities are normal to you, then you nothing to be concern of
If I had a video I could show you that its nothing to be of concern, not unless the eel is appearing as if its gasping for air, in which then you could have a problem, but also is a minor one.
Eels need a variety in their diet and boalgf, for what this be worth to you, I never feed only 20 shrimps for as in any one feeding for my own eels I feed them two types of foods and I change their meal the following with another two types of seafood's for which at most, I not so often feed the same type of food back to back (week).
For even young juvenile eels if are small fish eaters, one can feed them octopus. I feed octopus to my goldentails and when they reef tanks do become ready in which right now I little problem is there. I will be feeding octopus to the dwarf eels I will have. For one must try to put in their eels diet as much a variety in types of foods. This in the long term as all else one needs to do would prove far better for anyone's eels health.