I have heard that fish need fruit and veg. What kind of preperation should be done to these vegg. and fruit. Should all of it be fresh such as fresh spinich or can it be unsalted canned spinich. do they like grapes? and is any type of fruit and vegg. unsafe?

Any type of fruit and veg is fine. Fresh is best, as it is for us too, but frozen is also fine (defrosted obviously!). You need to be more careful with tinned things because they often have salt or sugar added.
If the fruit or veg has a skin (like grapes) it needs to be peeled, or in the case of peas, popped out of their shell. Then just chop into tiny bite sized pieces. If you are feeding hard veg (like swede, potatoe etc) then cook it slightly first to soften it.
All fish have individual tastes so it's a case of trial and error really. All of my fish love grapes, swede, peas, apple, banana, romaine lettuce, sprouts and brocolli. Some of them like tomato, and some kiwi fruit. You'll just have to experiment!
I wouldn't feed fruit or veg more than a couple of times a week though.