It's interesting to see how fish differ in their dietary preferences. I bought some frozen Tubifex worms a few weeks ago, and offered them to my fish. The occupants of the Macropodus tank immediately went crazy over the stuff. On the other hand, in the main tank no one but the Panda corys and the neon tetras showed much interest in it initially. Over time most of the other fish have learned that this is food, but only the pandas would go after it when anything else is present - and the Macropodus still don't realise that Tubifex worms are food. It's odd, given that their siblings are the ones that are most eager to eat it.
I noticed that the leaves of the 'Water wisteria' (Hygrophilia difformis) in the Macropodus tank have been chewed on, so I decided to see how they would respond to blanched spinach. Again, unlike their siblings in the main tank, they went after it enthusiastically. So finally, I offered them blanched zucchini. Twelve hours later it sits untouched at the bottom of the tank. I also added some zucchini to the main tank for the Otocinclus. Much to my surprise, one Macropodus and one cory took a liking to zucchini.
I find it interesting the way that dietary preferences differ both among individuals and within the "culture" of a tank. The Macropodus in the main tank and those in the Macropodus tank are "littermates" and full siblings. And yet they differ in terms of their willingness to take food items. Competition for food is more intense in the Macropodus tank, so it isn't surprising that they would more readily take any food item offered. But why do their siblings in the main tank totally ignore the same food item? The zucchini issue shows another level - that of "personal" food preference.
While I added zucchini primarily for the Otocinclus, the only other fish I have seen eating from it was one of the kuhli loaches.