Hydor Theo 300W Submersible Aquarium Heater fit check
Hydor Theo 300W Submersible Aquarium Heater is a 300W shatter-resistant glass submersible. ReefCrafter's 2.5-5 watts-per-gallon band puts it at roughly 60-120 gallons of display water, before room temperature and redundancy choices. At this wattage a controller or a split two-heater setup limits the damage of a stuck-on failure.
Hydor Theo 300W Submersible Aquarium Heater: fits roughly 53-80 gallon systems. Specs, compatibility math, sizing risks, and alternatives before you buy.
Who it is for
Good fit for
- ✓ 53-80 gallon systems, per the catalog fit range.
- ✓ Roughly 60-120 gallons of display water at 2.5-5 W per gallon.
Not a fit for
- ✕ Tanks under about 53 gallons; it is sized above them.
- ✕ Systems over about 80 gallons without adding capacity elsewhere.
- ✕ Running alone on a large tank without a controller; split heat or add a controller.
Compatibility math
Safe wattage band
Example: 300W is usually a planning fit for roughly 60-120 gallons before room-temperature and redundancy choices.
ReefCrafter checks both the low-wattage failure and the oversized stuck-on failure.
Risk notes
- A single oversized heater can cook livestock faster than a beginner notices the problem.
- High wattage should be split or controller-protected on most reef systems.
Professional fit context
- Check wattage, controller, redundancy, tank size, and whether two smaller heaters are safer.
- Hydor Theo 300W Submersible Aquarium Heater fits roughly 53-80 gallon systems; confirm that range against the final display volume, sump volume, and livestock plan.
Alternatives to compare
- Aqueon Pro 300 Adjustable Submersible Heater 300W
Same 300 W; compare format and features instead.
- Bulk Reef Supply BRS 300W Titanium Aquarium Heater System WiFi
Same 300 W; compare format and features instead.
- Bulk Reef Supply BRS Titanium Heater Element 300W (no controller)
Same 300 W; compare format and features instead.
Full spec snapshot
- Category
- Heaters
- Build tier
- Balanced
- Estimated price
- $48
- Tank fit range
- fits roughly 53-80 gallon systems
- Format
- Shatter Resistant Glass Submersible
- Heater wattage
- 300 W
Related reading
Questions
What size tank is a 300W heater like the Hydor Theo 300W Submersible Aquarium Heater for?
ReefCrafter's 2.5-5 W per gallon band puts 300W at about 60-120 gallons. Cold rooms push toward the smaller end; tanks over 50 gallons are safer with two smaller heaters.
What tank size is the Hydor Theo 300W Submersible Aquarium Heater for?
ReefCrafter's catalog fit range for it is 53-80 gallon systems. Confirm that against your final display volume, sump volume, and livestock plan rather than the box label alone.
What should I compare the Hydor Theo 300W Submersible Aquarium Heater against?
Aqueon Pro 300 Adjustable Submersible Heater 300W (Same 300 W; compare format and features instead); Bulk Reef Supply BRS 300W Titanium Aquarium Heater System WiFi (Same 300 W; compare format and features instead); Bulk Reef Supply BRS Titanium Heater Element 300W (no controller) (Same 300 W; compare format and features instead).
Similar fit checks
