"HMX 300W" Titanium Housed, Plastic Protection Guarded, High Temperature Stability Aquarium Heater with Digital Touch-Sensitive Controller (Average Temp Variance from Set Temp = 0.4°F┃On/Off Temp Swing = 0.25°F)
"HMX 300W" Titanium Housed, Plastic Protection Guarded, High Temperature Stability Aquarium Heater with Digital Touch-Sensitive Controller (Average Temp Variance from Set Temp = 0.4°F┃On/Off Temp Swing = 0.25°F)
"HMX 300W" Titanium Housed, Plastic Protection Guarded, High Temperature Stability Aquarium Heater with Digital Touch-Sensitive Controller (Average Temp Variance from Set Temp = 0.4°F┃On/Off Temp Swing = 0.25°F)
"HMX 300W" Titanium Housed, Plastic Protection Guarded, High Temperature Stability Aquarium Heater with Digital Touch-Sensitive Controller (Average Temp Variance from Set Temp = 0.4°F┃On/Off Temp Swing = 0.25°F)

"HMX 300W" Titanium Housed, Plastic Protection Guarded, High Temperature Stability Aquarium Heater with Digital Touch-Sensitive Controller (Average Temp Variance from Set Temp = 0.4°F┃On/Off Temp Swing = 0.25°F)

Brand: Finnex
Item Number: FNNX-HMX300S

Regular price $47.99 On Sale

Only 10 left in stock!

Estimated Arrival: Between Apr 12 and Apr 18. *ETA for USA only. For accurate lead times, call us at 727-214-7750

Large, Custom, Or Backorder: Arrival Times May Vary.

Shipping Policy: Little or No Shipping Charges for Regular-Sized Items; We Cover Part of the Freight Costs for Large Items Shipped Nationally. See Shipping Policy.

Heater Height: 11.8"

Average Temp Variance from Set Temp: +/- 0.4°F

On/Off Temp Swing: 0.25°F

Temp Control Range: 68-92°F

Recommended Tank Size: 80-100 Gallons

Power: 300W / 2.7A


  • Titanium Body with Protective Plastic Guard creates virtually unbreakable unit that is nearly impossible to corrode or rust
  • No Moving Parts increases longevity and minimizes failure risk
  • Included Digital Touch-Sensitive External Heater Controller keeps hands dry and makes adjustments easy
  • Built-In Controller Memory restores previous heater settings and temps after a power outtage
  • Fully APEX Compatible

What's Included:

  • (1) HMX 300W Titanium Housed Aquarium Heater with Attached Plastic Guard
  • (1) HMX Digital Heater Controller
  • (1) Clip-On Heater Holder with Suction Cups

Note on the Importance of Properly Sized and Functioning Aquarium Heaters: A very important aspect to choosing the correctly sized and powered aquarium heater for your system is called Temperature Ambiance. Essentially, technical talk for - consider the environment and temperature conditions where you live...

  • Some live in climates that are quite warm all year round, so they may not require the recommended heater size for their system as described in the guideline above, and can be safe to go with a slightly lower wattage than the guideline above as to not overshoot on heat generated. These hobbyists may want to pick up an Aquarium Chiller as well to ensure that their tank can be cooled if needed.
  • Others live in climates that remain quite cold year round, so they may consider choosing a heater that is slightly above the recommended heater size guideline for their system as described above, so they can have a bit of extra juice when winter rolls around.
  • Others live in climates that are warm half of the year, and cool the other half, in which case we'd advise getting two or more heaters for their system that evenly split the difference between the recommended heater size guideline for their system, and set one to turn on at the lowest temp they'd like their aquarium to be kept, and the others 2° cooler than that (Ex: Heater 1 = 78°, Heater 2 = 76°). That way, full wattage is only being used when needed, and the system temperature remains flexible.

This is also important to consider for the immediate environment of the tank. Do we usually keep our home, office, or room that our aquarium is in warmer or cooler? We can follow the same guidelines above to help determine what's best for temperature control of the tank's immediate environment.

Heaters are one of, if not the most common reasons for failed aquariums, because of either failing on (heating up the aquarium and cooking the tank), or failing off (not turning on and freezing out the tank). We make sure to only list the most reliable heaters that have been tested over many years in many different systems and environments all over the globe. However, as with any electronic aquarium equipment, there's always a chance of failure, which in the case of heaters is catastrophic.

For this reason, we strongly advise to fully replace your tank's heater system every 12 months. This will ensure that the delicate instruments that cause the heater to function properly are always fresh and in peak operating condition when in the aquarium, to minimize risk of failure and maintain a successful aquarium life support system. It's been our experience that the few extra bucks saved by holding off on a heater replacement for a few more months are far outweighed by the financial and emotional damage from a cooked or frozen out tank.

We also highly recommend that whenever an aquarium heater is purchased, it should be partnered with an Aquarium Heater Controller, which regulates the heater's function while also acting as a fail-safe if the heater fails on or off. Absolutely invaluable, and for the price, a very wise investment in the longevity and overall success of our system.

The final option to full-proof an aquarium heat control system is an Aquarium Thermometer. Some heaters come with a temperature indicator included, but to be honest, most of these are quite cheaply made and are not reliable in terms of accuracy or longevity. To bulletproof your setup, invest in a quality Aquarium Thermometer to act as a standalone visual indication of the precise temperature of your water.

Some choose to invest in multiple heaters to partially fix this issue, but at the end of the day, we've found Annual Replacement Heater PurchasesAquarium Heater Controller Fail-Safes, and Aquarium Thermometers to be more effective and full-proof. However, multiple heater investments are especially effective at higher tank sizes (anything 150 gallons or above).

Heaters are a very important and often overlooked topic in the aquarium industry. If you're still unsure of what exact heater size and wattage will be best for your system or what equipment is needed to full-proof your system, visit the "Questions" tab so we can advise on what heater will create the most successful aquarium for your individual situation.

Have any further questions that aren't answered here? We'd love to hear from you, and learn how we can help you be as successful as possible in this wonderful hobby.

You can call in to 727-214-7750 to speak with Tyler from our team to determine how to create your Ideal Aquarium Build.

Also feel free to reach out to us at info@twotidesaquariumsupply.com and we will aim to respond back within the next few hours.


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I’ve used these lights on my Nano Reef tanks for well over a year now so I decided to roll the dice and run four over my newly purchased Prostar 200 Aqaurium even though they aren’t intended for larger tanks. Paired with the 18 inch flex mounts these lights offer a clean high end look for under $1K. The best part is they can provide enough even solid PAR spread to run a mixed Reef tank if you plan accordingly. The app is easy to use when you get the hang of it and their website has plenty of presets that you can download to make set up a breeze. If your looking for a high end reef capable light without the high end cost and bulky appearance then this is a good choice.

Thank you Tyler for getting these to me quickly!

Really is a quality tank and stand at the best price I could find

I bought the ProStar 200 (150g) n white. It did take a while (5 weeks) for the tank to make it to Arizona, but it was worth the wait. The tank glass is burly, well beveled, and the black silicone seams are really well done. In my case I couldn't find a single thing wrong with the tank or stand on arrival.

Pre-installed plumbing + conversion kit (separate purchase) made the plumbing, including an inline UV sterilizer, super easy.

The stand is spacious, with a good sized sump while still leaving sufficient overhead space for taller equipment, mounting lights for a refugium, getting your hands into the different sump compartments, etc.

As almost every other review has mentioned - Tyler Moon really does show an extraordinary level of customer service throughout the experience - buying, setting up, and beyond. Fully expect frequent communication from him via text and phone call to make sure things are working out smoothly.

Another positive I thought I would highlight regarding circulation noise between sump and display. Everyone's system will vary, but I found the draining system with spiral silencer inserts and silencer caps to be very quiet. With a 2000 gph DC return pump I can strike a good balance between the return flow and gate valves on the pre-assembled drain lines such that I get super quiet draining as well as maintain the water height in the display that I want. With the return pump at 100% and the drain lines wide open I do get quite a bit of noise, but I am not looking for 2000 gph during normal operation from my return pump on a 150g tank.

Easy enough

The kit installs just like any PVC slip coupler - glue in place. Seems like good quality schedule 40. I'm sure there are logistical challenges, but just a thought - since the tank comes with preassembled plumbing for drain and return lines, why not add in the step of also using the conversion kit BEFORE shipping to customers? From what I've read and seen, it's basically impossible to get fittings in the US for the metric sizes the tank comes with. Someone is clearly already doing the pre-assembly. Ship them a box of the conversion kits and add that as a step to the pre-assembly.

Excellent Tank, Service and Shipping

The whole experience was an A+. As soon as the order was placed I got a call letting me know they were doing a QA check and getting it packed for shipping. A couple days later it was delivered on a freight truck. The shipping was fast and tank was packed very securely. The tank was beautiful and without any defects. I highly recommend two tides and will use them in the future.

Perfect in every way

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