IMO mandarins are the easiest, no maintenance, no work,no disease fish we can keep.
"If" we have the correct tank of the proper age and size.
They seem to live at least ten years, maybe longer, and spawn almost constantly.
But if you have to feed them, I don't think you will be that successful. A mandarin can find all the food it needs all by itself if the tank is correctly set up and not to clean or new.
Also, IMO you will not be successful if you think you can feed them frozen foods, even though they will eat almost anything small enough unless you want to feed them every minute or so.
They are like seahorses as they have a silly tube in them that they call a stomach. It can not really store food as that fish is designed to eat a very small creature every couple of seconds.
If they eat more, the food in their ridiculous gut just gets pushed out.
They need a tank with some "mulm" in it which is dying vegetation, detritus, and anything else that develops on the back and under rocks in an aged tank.
Forget keeping a mandarin for any length of time in a new or clean tank. (4 years is not any length of time)
Your 65 gallon tank is right on the verge of a tank that is to small but a mandarin should be able to live there if enough "natural" pods are in there. Not store bought pods because I doubt they will reproduce enough and you will go broke way before the fish dies of old age.
My tank is old but even there I sometimes throw in sinking pellets. Not for the fish as my fish won't eat those, but for the copepods that multiply like crazy as I have many pod eaters.
You can build one of my Mandarin feeders but even then, the tank needs to have enoughfood being produced on it's own.
They will eat blackworms and white worms as I am showing here with a device to keep other fish out. But this is not a long term solution.
Here is a feeder I designed for mandarins and other pod eaters. Almost all the fish in this video are spawning. But again, the tank needs to make it's own food.
Good luck