Coach against fish... hahaha...
First, if you don't know how to play against a fish you are a fish too.
I think that your opponent is a Loose Passive
Play like Tight Agressive
Choose stronger hands than him
Play in position
Never
bluff neither slowplay.
If you have a pair, control the pot and win a little pot
When you have a strong hand, make him puts all his chips on the table.
He ever pays with nothing, so when he becomes agressive, it is a bad signal
REMEMBER bad beats can be happen but you'll win more times.