What size heater do I need for a 29 gallon tank?

A 150-watt heater is the all-round pick for a 29 gallon tank. In a warm room 100 watts is enough; in a cold room step up to 200 watts. A 29 is small enough that a single heater handles it evenly, so one good 150-watt adjustable is all you need.

Is 100 watts enough for a 29 gallon tank?

100 watts is enough for a 29 gallon in a warm room with a small temperature rise. For an average or cold home, 150 watts is the safer all-round choice. Size for the coldest the room gets so the heater is not running flat out on winter nights.

Do I need two heaters for a 29 gallon tank?

No. A 29 gallon is below the roughly 50-gallon point where splitting wattage across two heaters pays off. A single 150-watt adjustable heats it evenly. Running two becomes worthwhile on 55-gallon and larger tanks for even heating and failure safety.

Best heater for a 29 gallon tank

Short answer: a 29 gallon tank wants a single 150-watt adjustable heater for a typical home — 100 W in a warm room, 200 W in a cold one. The best pick is a Cobalt Neo-Therm 150 or Aqueon Pro 150. A 29 is still small enough that one heater does the whole job; you don't need to split wattage yet.

The pick, in one line each

Best overall — Cobalt Neo-Therm 150 (150 W). Flat, shatterproof, and accurate to the degree — the most-recommended heater for this size. Adjustable, fully submersible, and easy to tuck behind a tall 29's back glass.
Best value — Aqueon Pro 150 (150 W). Shatter-resistant, dry-run auto-shutoff, and a dependable thermostat for the money. The safe default for a first 29.
Warm room — 100 W is enough. A home near 74°F only needs a small lift to tropical temperature; a 100 W adjustable covers it, with 150 W giving comfortable margin.
Cold room — step to 200 W. A basement or drafty room wants the extra headroom; a 200 W adjustable still holds a 29 safely if you run a thermometer.

Why 150 watts

The watts-per-gallon rule puts a 29 gallon between 100 and 200 watts — about 3 W/gal in a warm room, 5 W/gal where the rise above room temperature is large. A 29 shares the 30-gallon row on the wattage chart (the extra gallon is noise), so 150 watts is the all-round answer: enough to hold a cold night, not so oversized that a stuck thermostat is a hazard. The 29 is a popular first "real" tank — a community of tetras and corys, or a single centerpiece — and a steady 76–80°F is what keeps it healthy.

The tall-tank note: heat where the fish are

A 29 is a tall tank on a 30-inch footprint, the opposite shape from a long, shallow tank. That's mostly good — tall tanks mix and hold heat well — but it means you should mount the heater low, near the bottom third where warm water rises through the column, and ideally near the filter flow so the current distributes it. The one mistake to avoid here isn't wattage, it's trusting the dial: set 150 W to your target, then confirm with a separate thermometer at the far end and adjust over a few days. A 29 doesn't need two heaters — that's a 55-gallon-and-up decision — so put your effort into placement and an accurate reading instead.

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Cobalt Neo-Therm 150 (best overall) · Aqueon Pro 150 (value) · Fluval M150 (slim) · Digital thermometer (essential)

Wattage targets are a starting point, not a law. A well-insulated tank in a warm room holds temperature on less; a thin-glass tank in a cold room wants more. Size for the coldest the room actually gets, always run a separate thermometer, and adjust to what your tank does over a few days. Model suggestions reflect each maker's published tank-size rating and common hobbyist consensus, not a guarantee of fit for every setup.

Frequently asked questions

Is a 29 gallon the same as a 30 gallon for heater sizing?

Effectively yes. The single gallon difference is within the rounding of the watts-per-gallon rule, so a 29 and a 30 both take a 150-watt heater for a typical home.

What temperature for a 29 gallon community tank?

A stable 76–80°F suits most community fish. Set the heater there, verify with a separate thermometer, and fine-tune a degree at a time rather than trusting the dial.

Can I use a 200-watt heater on a 29 gallon?

Yes, especially in a cold room — it just has more headroom. The only caution is that a larger heater raises the tank faster if its thermostat sticks, so run a thermometer to catch a fault early.

Sizes either side: 20 gallon · 40 gallon · Full heater wattage chart · Heater calculator

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