The short answer for siamese algae eaters
Yes. The siamese algae eater is a river fish from the warm waters of mainland Southeast Asia, and it expects a heated tank in the mid-to-upper 70s Fahrenheit. Owners sometimes assume a fish bought as a hard-working cleanup crew member must be rugged enough for a cold tank; in reality this species' famous work ethic is temperature-powered. Warmed properly, a siamese algae eater roams all day, rasping algae from leaves, wood, and glass, including the tough black beard algae most other fish ignore. Cooled down, it parks itself, eats little, and leaves the algae to win.
A fish built by warm, moving water
In the wild, siamese algae eaters live in the rivers and streams of Thailand and the Malay Peninsula, holding station in gentle current over rock and wood, grazing constantly. Their flattened underside and underslung mouth are tools for clinging and scraping in flowing water, and their high activity level is fueled by a metabolism set for warm conditions. They also grow larger than many buyers expect — a well-fed adult becomes a substantial, powerful fish several inches long — which means the cool, small tank that tempts a beginner is wrong for them twice over: wrong temperature, and soon too little room. Warm water and space are the twin foundations of keeping this species well.
Setting up the heated river tank
Aim for 75 to 79 degrees Fahrenheit. Set the heater during the cycle and confirm the reading at the far end of the tank, since a long aquarium — which this fish needs — can run noticeably cooler at the end away from the heater if flow is weak. Position the heater where current washes past it, and add the tight-fitting lid at the same time: siamese algae eaters are accomplished jumpers, especially when startled, and a heated tank found empty in the morning is a heartbreak this species is known for. Check the temperature after large water changes, and if the fish shares the tank with other species, make sure the whole community's comfort ranges overlap in the upper 70s rather than bending the dial down for a cooler-water tankmate.
Reading the temperature from the fish's behavior
With this species, behavior is the thermometer you can see. A warm, content siamese algae eater is nearly always in motion — grazing a leaf, then a rock, then the glass, resting only in short pauses with its fins working. A cold one sits. If your fish is parked on the bottom for long stretches, ignoring algae it used to attack, check the thermometer before you change anything else; a failed heater is a common and quietly disastrous discovery. Overheating shows as frantic, skittish darting. If activity does not return within a day or two of restoring proper warmth, or the fish thins while tankmates thrive, that is the point to consult a veterinarian who sees fish or a specialist shop. Busy households are exactly where this fish's care slips, and KinsLe's Care Teams keeps its water changes, supplement feedings, and temperature checks assigned to named people, each marked done so nothing silently lapses.