You can get garlic essense at the grocery store, or you can just get minced garlic in water, and use that.
Doubt your oscar took an interest in cucumber. You're mostly going to have difficulty getting meaty treats to your melon. Shrimp pellets and the like. Which is ok, your melon needs more veggies than anything else.
My Ancistrus (bristlenose) get fed courgette every day; the sailfin plec three times a week or so, and the clown plecs twice a week as they're happier munching wood or bloodworms. With L330 I'd try and make sure he gets plenty of vegetables and bogwood to eat- if he eats everything over 24 hours I'd put some in straight away again. Large Panaque like him apparently also like potatos and peas.
ok i'll see how good of a pic I can get on monday. he has only eatin the zucc with the garlic. zucc by itself...nope! and lettuce has been on a clip for 2 days and he hasnt touched it yet. the other day i was feeding the oscar krill and being the messy eater that he is some large pieces fell to the gravel. the pleco came out of his cave to seek it out, ate it and went back to hiding.