Rather than cucumber (which has no nutrition and turns to mush) use something else. Courgette (=zucchini) works well and is a bit more nutritious. Even better are broccoli, carrot, and sweet potato. These are much more nutritious and contain less water. So they don't become mushy nearly so fast (carrot stay firm for days, even a week).
There's absolutely nothing wrong with trying a bit of whatever fresh fruit or vegetables you use during the week. Some plecs enjoy lettuce, others tomatoes, some even like raw potato. Spinach is always good, and frozen peas are especially nutritious. Other fish eat peas, too. I even have a pufferfish that likes them now and again!
I'd tend to recommend against microwaving, because that destroys some of the vitamins, partly because timing how long to zap the food for is tricky. Dipping something in boiling water ("blanching") softens vegetables without quite so much vitamin loss. You only need to wilt lettuce, not boil it. Many plecs (such as Panaque spp. and the larger Hypostomus spp.) can eat and digest unblanched vegetables just fine, and in fact the fibre content is very good for them. Certainly peas, spinach, and fruit shouldn't need blanching at all, and I don't bother with carrots, sweet potato, or courgette, either.
Above all else, be sure and add vitamin-enriched algae wafers to their diet, choosing a brand with vegetable/Spirulina rather than meat proteins. Too much meaty food is not good for many plecs. Also, bogwood is essential: some eat and digest it, others merely use it as fibre. Either way, plecs don't do so well without it.
Cheers,
Neale
