Feeding Vegetables To Fish ?

[madmonkey04]

Tank 1    100L :  6 glowlight tetras, 4 guppies, 4 red eye tetras, 2 golden balloon rams, 2 penguin tetras and one Melanistius Corydoras ohhh and one snail
 
Tank 2     40L :  10 Guppies
 
What vegetables can I put in both tanks and how should I prepare them.
Thanks Alexander

 

[fish48]

 Lettuce or spinage can be boiled    frozen ​ or tin peas, no need to boil } or slice cucumber.