Peaceful where it counts
A siamese algae eater spends its social energy on surfaces, not fish. It ignores tetras, rasboras, and other small mid-water species completely, passes over corydoras and loaches on the substrate without incident, and shows no predatory interest in anything it shares the tank with — even fry are generally beneath its notice while grazing food exists. Its movement is constant but purposeful, and shyer tankmates habituate to it quickly because the pattern never varies: graze, move, graze. As a community citizen in a well-sized aquarium, it is an easy large-ish fish to house.
Footnote one: lookalikes and rivals
The species' territorial instinct, such as it is, targets its own reflection in other fish — elongated, bottom-oriented grazers with a similar silhouette. Flying foxes, rainbow and red-tailed sharks, and other siamese algae eaters can all draw chasing and fin-flaring, particularly in tanks under four feet long. Kept as a group of five or more in a genuinely large aquarium, siamese algae eaters distribute that friction among themselves and settle; kept as a pair of rivals in a small tank, one will usually dominate. The simple community rule is one siamese algae eater per tank unless the tank is big and the group is bigger.
Footnote two: the crowded, hungry adult
Reports of siamese algae eaters sucking at the flanks of angelfish or discus almost always involve an adult in a tank that is too small, too clean, or both. A grazing fish with no algae, no wafers, and no vegetables will improvise, and the slime coat of a slow, flat-bodied neighbor is the improvisation. It is a husbandry signal rather than a character flaw: feed the fish deliberately, let soft algae persist on hardscape, and the behavior rarely appears. This is also where the species is confused with the Chinese algae eater, which develops the habit as a matter of course — check the unbroken stripe through the tail before blaming a true siamese algae eater.
Building a community around one
Give a siamese algae eater the run of a forty-gallon-plus tank and it complements almost any peaceful roster: mid-water schools above it, corydoras beneath, a gourami or angelfish as centerpiece provided the grazer is well fed and the tank has length. Plants do double duty, offering grazing area and visual breaks that dissolve the few chases that do occur. Avoid pairing it with other dedicated algae-eating bottom fish competing for the same surfaces unless the tank is large; a bristlenose in a six-foot tank is a colleague, while the same pairing in three feet is a rivalry.
The observation habit that keeps the peace
Peaceful is a condition you maintain, not a trait you purchase. Watch the first weeks after any new bottom-dweller arrives, confirm your algae eater is finding wafer and vegetable food at lights-out, and check slow tankmates' flanks when you feed. If chasing appears, more structure, more food, and more space are the levers — in that order — before rehoming anyone. Sketching the new layout on paper first saves both fish and tempers, so put a follow-up question to KinsLe's Kinny before moving anyone; he answers using the KinsLe Answers library.