These freshwater fish are herbivores. Wild otocinclus would constantly graze on any available plant matters, not just algae.
Meanwhile, in captivity, a well-balanced tank often doesn’t produce enough soft algae to sustain a group of otocinclus. Even though they prefer algae, they’d be more than glad to munch on some cucumbers.
Before feeding your otocinclus, make sure to blanch the cucumbers. That way, you don’t accidentally introduce harmful bacteria to the tank. Then, slice the cucumbers into thick slices so your otocinclus can enjoy them more easily.
Besides cucumbers, otocinclus love eating other fresh vegetables, including spinach, lettuce, zucchini, and Brussel sprouts.