Question: Axolotl Won't Eat Anything

I've never posted on here and I've looked all over for an answer to this but it seems that not many people have this problem. This is going to be long so please bear with me.

I think I own the worlds pickiest axie. I can't get him to eat anything. He's not sick from what I can tell. I've owned him for about a year now and he has always been like this. I'm just really frustrated. He's my first axolotl and I don't know what to do. He won't eat anything. A little info about my tank- I have a 20G long. Only one axolotl in the tank. I use a sponge filter with the air pump on the lowest setting so there's really little flow in the tank but there's still oxygen being pumped into the tank. The temperature is always in the low 60's. All my water levels are perfect. I do weekly water changes to ensure that they're always good. Back to him not eating, all he will eat (and only when he feels like it) is bloodworms. He's so thin and will not eat anything I feed him. I've tried various pellets, bloodworms, mysis, salmon, minnows, crickets (I know there's debate over whether they're safe or not but I'm desperate) and more. The breeder claims he didn't have any issue with him and fed him pellets but he came to me very thin. He acts completely normal, so like I said earlier, I don't feel like anything is wrong with him health wise. I have tried fridging him many times to see if it would help and it doesn't.

Any ideas as to what I should do? I don't think he can live a healthy life only picking at bloodworms every so often. Any help or ideas at all will be a huge help. Thanks in advance.

Have you tried earthworms or nightcrawlers? I got my axie off bloodworms at like 3 inches and got him onto earthworms and then very quickly swapped to night crawlers which caused him to grow quickly.

Usually I have to take the live worm, shove them into boiling water to kill it and then a quick rinse in cold water. Thats the only way he will take worms.

I've had great success with live blackworms (ordered online or sold at local fish stores) and live red wigglers (from Walmart's fishing department). Live blackworms are like crack for axolotls. Some axolotls apparently don't like the slime coat taste on red wigglers, but I just rinse them first in a cup of water and my 8-9" axies find them easier to swallow than giant nightcrawlers (plus then I don't have to cut them up).