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Finnex Max-300 Digital Aquarium Heater Controller

by Finnex
4.1 out of 5 stars 57 customer reviews
| 18 answered questions
List Price: $29.99
Price: $28.90 & FREE Shipping on orders over $49. Details
You Save: $1.09 (4%)
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Ships from and sold by Amazon.com. Gift-wrap available.
  • LED Heating Indicator and Current Temperature Thermometer
  • Over Heating Protection +Memory
  • Safely Monitors Heaters up to 300 Watts
  • Not compatible with Aqueon PRO heater series. Finnex HC810M or HC800 controller recommended for such
  • Heater sold separately
  • LED Heating Indicator and Current Temperature Thermometer
  • Over Heating Protection +Memory
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4 new from $23.90 1 used from $16.75
$28.90 & FREE Shipping on orders over $49. Details In Stock. Ships from and sold by Amazon.com. Gift-wrap available.

Frequently Bought Together

  • Finnex Max-300 Digital Aquarium Heater Controller
  • +
  • Hydor ETH 300 In-Line External Aquarium Heater, 300w, 5/8" hose
  • +
  • HDE LCD Digital Fish Tank Aquarium Thermometer
Total price: $84.82
Buy the selected items together

Special Offers and Product Promotions

  • Buy Used and Save: Buy a Used "Finnex Max-300 Digital Aquarium Heater Controller" and save 44% off the $29.99 list price. Buy with confidence as the condition of this item and its timely delivery are guaranteed under the "Amazon A-to-z Guarantee". See all Used offers.

Product Details

  • Product Dimensions: 3.5 x 1 x 2.3 inches ; 12.8 ounces
  • Shipping Weight: 1 pounds (View shipping rates and policies)
  • Domestic Shipping: Item can be shipped within U.S.
  • International Shipping: This item can be shipped to select countries outside of the U.S. Learn More
  • ASIN: B007480AP6
  • Item model number: HC-0300M
  • Average Customer Review: 4.1 out of 5 stars  See all reviews (57 customer reviews)
  • Amazon Best Sellers Rank: #41,395 in Pet Supplies (See Top 100 in Pet Supplies)
    • Manufacturer’s warranty can be requested from customer service. Click here to make a request to customer service.

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Customer Reviews

Top Customer Reviews

5.0 out of 5 starsAccurate, easy to use, good price.
By Threedog on October 21, 2014
Verified Purchase
Received the controller very quick. 2 days, including a Sunday. Very simple to use, which is good since the instructions are not great. The temperature probe is spot on with my other digital thermometer in the aquarium. I did a third verification with another thermometer I use. If I had to make any suggestions, it would be the length of the probe cord. I have a 48" long tank, with the heater on one end and the temp probe on the other, it works fine, but no room to spare. If you go much over the 48" tank length, Your heater and probe may not make it to opposite ends of the tank. Other suggestion; on the frame of the controller, there is a hole to screw it into... tank stand, wall, whatever... That hole is so close to the out-coming wires that it will be really difficult to get a screw into the hole and screw it in with the wires in the way. Product includes a hanger. I assume that's what it's for. Though it was too small to hook on the rim of my aquarium.
Overall, excellent product and a good price.
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5.0 out of 5 starsPerfect solution for aquarium heater issues
By Linda A. on February 6, 2015
Verified Purchase
These things are great! Our house is very cold in winter and hot in summer. Therefore, we use relatively high power low cost all-in-one aquarium heaters (200-250 watts) in winter to keep the tanks warm. Those same heaters over-heat the tanks in summer and means we're constantly fiddling with the settings. Instead, I have one of these controllers on each tank. I set the heater in the tank so that on it's own it runs about 81 degrees in the coldest conditions. Then I hook it into this controller, set the controller to 79 and from that point on my tanks never vary more than 1 degree from the set point. I figure if the controller fails always on the internal thermostat in the heater will still keep it from cooking the fish and if it fails open circuit the temperature display and alarm will warn me before it is too late. It's helpful to place the remote sensor about 1/2 of the tank length away from the heater and not on the side that would get direct sunlight or near a radiator.

The LED indicators tell you when there is power going to the heater and if there is power on the controller. This even makes water changes easier because all I do is turn the controller off with a button push to disable the heater during the water change. You can mount these with double-sided foam tape directly on the tank or hang them on the wall from 3M Command strip wire hooks. Either way they are easy to install and operate.

We've only had them a few months so can't say how long-term reliable they are but they use solid-state relays so they should last a while. I'll post here again if we ever have an issue. Good peace of mind for small money right here!
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5.0 out of 5 starsInexpensive peace of mind!!!
By T. M. on April 5, 2013
Verified Purchase
I've added a Finnex Max-300 Heater Controller to my 75 Planted Aquarium after a new heater malfunctioned. The additional peace of mind is worth every penny of the $30 investment. I feel good knowing that if I have a heater stick, the Finnex Max-300 will be there protecting my aquarium. Considering we put significant amounts of money into our aquariums, what's another $30 to look over the safety our fish, shrimp, corals, and plants? So far, I've had this heater controller for 2 weeks and it is functioning flawlessly. I am very happy with my purchase and will be adding this as standard equipment to future aquariums.
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3.0 out of 5 starsInaccurate Readings/Calibration
By Bill Scott on May 12, 2014
Verified Purchase
The unit I received showed 73 degrees F after I let the probe adjust for at least half an hour. I used 3 accurate digital thermometers and they all read between 76.1 and 76.6 degrees F. I set the thermostat for 77 using a 150w heater in my 90 gallon reef tank. Very shortly thereafter my 3 test thermometers went to 80+. So the temps were off by 3 degrees. I found that if I set the device at 74 degrees and the water temp showed 73-74 degrees the water did maintain at 77 degrees. I tested this over a 3 day period of time.

I give the unit 3 stars as it did maintain my temp once I figured out that it was out of calibration. (You cannot manually calibrate the device.) Also, the digital readout is clear and easy to read. I ended up sending the unit back this morning as the 3 degree discrepancy just bugs me. I am going to order another one to see how that works out.
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5.0 out of 5 starsFantastic heater controller
By Magicjynx on August 11, 2012
Verified Purchase
I have 7 2.5 gallon tanks on a 45" piece of 11" flexwatt heat tape. This heater controller has kept every single tank at a perfect 80F with a variance of only 1 degree.

I can't say anything about its longevity, but within 5 mins of me setting it up, I bought a second. This was extremely easy to set up, and the fish love it!
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4.0 out of 5 starsSo far so good
By James Bauer on April 30, 2013
Verified Purchase
The controller was easy to install and setup. It has been keeping track of my Reef tank temp without a problem. The only negative I can think of is that it does not display tenths of degrees. If it did that I would give it five stars.
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1.0 out of 5 starsThe quality control of this product is not quite good as evidenced by the positive reviews and also the ...
By Bo on March 9, 2016
Verified Purchase
The quality control of this product is not quite good as evidenced by the positive reviews and also the negative ones. I do not write many reviews because most of the stuff I order are in good working order.

I ordered this one and received a week ago. Immediately I found it has the freeze up problem as mentioned by a few previous reviewers. http://www.amazon.com/gp/customer-reviews/RM9UGQ5BHQ8QC/ref=cm_cr_arp_d_rvw_ttl?ie=UTF8&ASIN=B007480AP6

Mine would cut off the power before the set temperature is reached. And when that happens, even if I raise the set temperature way up (like 10 degrees above the water temperature), it would still not power the heater.

If I turn off the controller and then back on again without touching anything else, it would power the heater.

It happened twice within a few hours so I would not use or recommend this unit. I did contact the company and they want me to send the unit to them to examine. I would be out of some shipping cost for a $25 item so I decided to initiate the return process to Amazon.

After some more readings, I decided to order an IFC-1000 controller and I will DIY with some wires. It seems to be more heavy duty.

For the records, I have a 15 year old analog Computherm (made by Otto), it is till working flawlessly for my turtle tank.
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Most Recent Customer Reviews

4.0 out of 5 starsgives unregulated aquarium heaters regulation and owner peace of mind!

Just what was needed to help give regulation back to an erratic aquarium heater. I'm glad I discovered this device before I cooked my fish. Read more

Published 16 days ago by Little T
5.0 out of 5 starsRegulates the heater like a dream

Works with my ancient Ebo-Jager, which finally lost its thermostat controller. Regulates the heater like a dream.

Published 29 days ago by Amazon Customer
5.0 out of 5 starsGreat product to regulate temperature

Great product to regulate the temperature in the small tank for my beta fish, especially when the tank is in a place where it can get very cold. Read more

Published 1 month ago by Zero2Heero
5.0 out of 5 starsFive Stars

Good safety for most heaters. work as described.

Published 2 months ago by Jiravat Wangwongvivat
3.0 out of 5 starsGet the 800 watt

Not that great for bigger tanks. Get the 800 watt, it has a better, more reliable relay for turning on/off heaters for many cycles over time.

Published 2 months ago by BigXor
5.0 out of 5 starsHe is very happy with the product

Bought 2 for my sons fish tanks. He is very happy with the product. He says it's built good. He would like to get one more for his third fish tank.

Published 2 months ago by Amazon Customer
5.0 out of 5 starsPeace of Mind is Priceless.

Very reliable, keeps me from worrying about my heater failing.

Published 3 months ago by Guy Miller
5.0 out of 5 starsConsistent, reliable, durable, overall good product!

I have had this for several months now, I was having some big swings in my 28g nanocube reef, 5 degree's plus, so got this, it consistently keeps the temp within 1 degree... Read more

Published 3 months ago by Marty M.
5.0 out of 5 starsFive Stars

Keeps my water at the perfect temp setting

Published 3 months ago by Raymond Lee
5.0 out of 5 starsAdds Safety and Keeps Temp Within a Degree

Working well. Using it with a Hydor inline 200w heater for a 30 gal aquarium. Keeps it within a degree of set temp. Read more

Published 3 months ago by Software Guy

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