Certain player, huge fish, hardly knows the rules, every time he folds his hand he just says fold.
Is there some rule saying he should throw his hand, or does the dealer have to reach every single time (to seat 3) and muck his cards like a b**ch?
How do you handle this?

The first time I grab them. The next time, I grab them. Then I look for an opportunity to not grab them as though I didn't hear him say fold, and when I tell him "Oh, I didn't want to take your cards. I never want to be the dealer that mucks someones aces while they're thinking! You can just toss them forward if you're folding so I don't make any mistakes."

Or you can sit there and wait and have everyone ask what the hold up is and you can tell them all that you're waiting for seat 3 to toss in his cards because you can't reach them.

Or you can passively aggressively cheerfully say "I'LL GET 'EM!" and over-act a big reach over to his side of the table and make groaning noises as you stretch out to get them.

Or you can just say "Can you toss those in a bit when you fold so I can reach them a little easier? Thank you."

Is he friendly? If he doesn't know the rules, he's also unlikely to understand etiquette so simply telling him that is is customary to discard the hand closer to the dealer to keep the game flowing seems reasonable.

If he's an *******, then Lord_Crispen has several worthwhile suggestions.

Well, I don't think Leha is concerned with the fish as much as being seen as rocking the boat by the others in the game. But that's just my read.

I was actually concerned with my back
Seat 3 is a big stretch...

I don't see any reason not to just ask him to slide them a bit forward then.

Yep, especially if you have a 'betting' line on the table. A simple request to slide the cards to the betting area is not out of line ... and be glad that you get to move on after the down? Maybe pass on the information to the incoming dealer to 'help' the other players keep this guy at the table longer. GL

Have seen folks in home games say fold but keep their cards close. Usually it is to show what a good fold they made to others or some other stupid reason. Maybe this guy is used to doing that at some home game or room and needs to be politely encouraged to push his mucked hand forward. It is important not to embarrass or upset a player that is good for the rest of the table , so diplomacy rather than enforcement.

I have short arms, so i usually just lean toward it and say to the guy "could you help me out, please? I have T-rex arms." It always gets a laugh and they tend to get the message.

Maye just say "throw them in, buddy" ?

I know, that was an easy one but don't worry at all. That's what we're here for.

Thanks for being here bud
Thats what i did in the first couple of times.
Problem was he was rather stupid+ didnt seem to remember/care for what i asked him to do, so my question was whats next.

Have the dealer deal his hand out of reach while saying "dealt" in a loud voice.

I go with a puzzled look and ask, "Are you mad at the dealer?"