Mechanical damage caused by herbivorous fish or snails is often misdiagnosed as nutritional deficiencies, particularly confused with a lack of potassium. However, the margins of the holes created by animals have sharp, jagged edges or translucent scrapes, unlike deficiency necrosis which has yellowed, faded borders. Loricariids (like Ancistrus and Plecostomus) tend to scrape the top layer of the leaf epidermis, particularly on Echinodorus, leaving a network of intact veins. Snails and fish like Cichlids or herbivorous Characins bite off entire pieces of the leaf.

Presence of holes with sharp or jagged outlines, without yellow halos around them. Broad leaves (e.g., Echinodorus, Anubias) present translucent scrapes where only the venous structure is visible (leaf skeletonization). Unlike potassium deficiency, holes can appear anywhere on the leaf and do not necessarily start from small necrotic 'pinholes'. New leaves may be eaten as soon as they emerge.

The direct cause is the presence of fauna incompatible with a planted aquarium. Species like Ancistrus, Plecostomus, Metynnis, some snail species, and various African or South American Cichlids consider aquatic plants a primary food source. Often these behaviors increase if the fish are not fed a diet sufficiently rich in plant fibers.

The definitive treatment consists of isolating or removing the species responsible for the damage. If removal is not an option, providing abundant substitute feeding is crucial: spirulina-based bottom tablets or blanched vegetables. In case of snail infestation, natural predators (like Anentome helena snails or Botia fish) can be introduced.

Before setting up a planted aquarium, carefully research the compatibility of fish species. Avoid introducing fish known to eat plants. Opt for aquascaping-safe species, such as Otocinclus, Corydoras, shrimp, and small Characins or Cyprinids.