Penn-Plax Cascade Heat Aquarium Heater – Fully Submersible – Great for Freshwater and Saltwater Fish Tanks – 7.5” Length – 25 Watt
$12.68




Price: $12.68
(as of Oct 13, 2025 11:42:00 UTC – Details)
Cascade presents the 25W LED Aquarium Heater by PENN-PLAX.
This heater easily maintains healthy water temperature within a 1° accuracy,
and can be set anywhere between 68 ℉ and 89 ℉, by using the red control knob.
Our Cascade Aquarium Heaters are factory set to 76 ℉,
and are safe for either freshwater or saltwater fish tanks.
The 25W model works great for fish tanks up to 5 gallons.Visible & Accurate Temperature Scale:
With an easy to read setting scale in both Celsius and Fahrenheit,
it’s easy to see the temperature adjustments being made.
To increase the temperature, rotate the control knob counter-clockwise,
and to decrease, rotate it clockwise;
or, follow the + and – symbols located near the control knob.
Orange Pilot Light:
Our Cascade Heat Aquarium Heaters feature a pilot light that indicates the heating cycle status.
This means that it will go on and off by itself as the thermostat cycles the heating element on and off.
In other words, orange light = heater is on.
Similarly, these aquarium heaters make a faint click when turning off.
Additional Features:
In addition to being composed of heavy-duty and shock-resistant glass,
these fully submersible aquarium heaters can be placed either horizontally or vertically.
There’s also a built-in minimum water level indicator at the top, colored in red.
Please Note:
Do not operate heater outside of aquarium, and never submerse a hot heater into an aquarium – only submerse a cool heater.
After placing the heater into your aquarium, wait 15 minutes before turning on.
This allows the thermostat to adjust itself to water temperature.
Measurements:
Overall Length = 7.5”
Overall Diameter = 1.1”
Suction Cup Diameter = 1.25”
Wattage = 25W
Voltage = 110V
Is Discontinued By Manufacturer : No
Product Dimensions : 7 x 1.5 x 3 inches; 7.83 ounces
Item model number : CH825
Department : Unisex-Adult
Date First Available : March 24, 2011
Manufacturer : Monster Pets
ASIN : B004TUKEZ8
Best Sellers Rank: #182,854 in Pet Supplies (See Top 100 in Pet Supplies) #367 in Aquarium Heaters
Customer Reviews: 4.1 4.1 out of 5 stars 280 ratings var dpAcrHasRegisteredArcLinkClickAction; P.when(‘A’, ‘ready’).execute(function(A) { if (dpAcrHasRegisteredArcLinkClickAction !== true) { dpAcrHasRegisteredArcLinkClickAction = true; A.declarative( ‘acrLink-click-metrics’, ‘click’, { “allowLinkDefault”: true }, function (event) { if (window.ue) { ue.count(“acrLinkClickCount”, (ue.count(“acrLinkClickCount”) || 0) + 1); } } ); } }); P.when(‘A’, ‘cf’).execute(function(A) { A.declarative(‘acrStarsLink-click-metrics’, ‘click’, { “allowLinkDefault” : true }, function(event){ if(window.ue) { ue.count(“acrStarsLinkWithPopoverClickCount”, (ue.count(“acrStarsLinkWithPopoverClickCount”) || 0) + 1); } }); });
FULLY SUBMERSIBLE AQUARIUM HEATER: The 25W Cascade Aquarium Heater easily maintains healthy water temperature within a 1° accuracy, and can be set anywhere between 68 ℉ and 89 ℉, by using the red control knob. The 25W model works great for fish tanks up to 5 gallons.
VISIBLE & ACCURATE TEMPERATURE SCALE: With an easy to read setting scale in both Celsius and Fahrenheit, it’s easy to see the temperature adjustments being made. To increase the temperature, rotate the control knob counter-clockwise, and to decrease, rotate it clockwise; or, follow the + and – symbols located near the control knob.
ORANGE PILOT LIGHT: Our Cascade Heat Aquarium Heaters feature a pilot light that indicates the heating cycle status. This means that it will go on and off by itself as the thermostat cycles the heating element on and off. In other words, orange light = heater is on. Similarly, these aquarium heaters make a faint click when turning off.
ADDITIONAL FEATURES: In addition to being composed of heavy-duty and shock-resistant glass, these fully submersible aquarium heaters can be placed either horizontally or vertically. There’s also a built-in minimum water level indicator at the top, colored in red.
MEASUREMENTS: Overall Length = 7.5” / Overall Diameter = 1.1” / Suction Cup Diameter = 1.25” / Wattage = 25W / Voltage = 110V
Customers say
Customers find the aquarium heater works well, particularly for 5-gallon betta tanks, and appreciate its accurate temperature control, with one customer noting it stays within 2 degrees of their tank thermometer. The product receives positive feedback for its size, being perfect for 5.5-gallon tanks, and customers like its adjustability and value for money. The suction cup quality receives mixed reviews, with some customers praising the great suction while others note the product doesn’t come with them.
12 reviews for Penn-Plax Cascade Heat Aquarium Heater – Fully Submersible – Great for Freshwater and Saltwater Fish Tanks – 7.5” Length – 25 Watt
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$12.68
Ladderman –
Awesome heater
First of all I recomend reading the 3 star March 7 2018 review . I have the 25w heater in a 5.5 G tank. As the reviewer recommends, I keep the room temperature fairly constant. I vave been through 4 heaters within a month: one just kept on cycling higher and higher until it would have cook my fish if I had them in there before testing the heater, another one warned that it could not be used with a light on the tank and the readings bounced all over the place, the third one I kept as a spare as it was too bulky, finally I happened upon this one which I have had for over a month now. This heater is very consistent, I set it up to heat the tank to 78,8°F before shutting off, and it will consistently wait until the tank cools to 78.3°F and then turn on and reheat the tank to 78.8°F, over and over. The only thing one must do initially is check the heater against a thermometer as the scale on mine was off by two degrees, but once compensated for it performs perfectly. For under $12.00 it’s a steel, is accurate, adheres, well, has a good chord, the adjustment know functions well, the heat indicator light is large enough to see, and fits nicely between the hob and corner of the tank. Finally a heater.
R. Lieberum –
Water Heater
Bought this to heat our 3-gallon fish tank. After letting it sit for 24 hours the water temperature was nearly perfect. I verified the water temperature with 3 calibrated thermometers and all were with-in half a degree of each other. This heater works very well and turns off once the set temperature is reached and will turn on if the water cools too much. I have it set for 77 degrees in order to keep our Betta comfortable. So far this fully submersible heater work very well and the 2 suction cups work just fine in the water. Only time will tell how long those will last. Happy so far.
Brooke H. –
Pretty great with MINOR flaws
I purchased this heater about 2.5 weeks ago and overall I think itâs a great heater for the money. This is one of the only heaters I saw on amazon that didnât âcook a fishâ. When I first received it, it was a little bigger than expected, but thatâs not really a huge problem for me. I have it in a 3 gallon tank for my betta fish & it doesnât take up too much room. I have it positioned sideways on the back of his tank mid-way down. Iâve had my betta since January and honestly never bought a heater for him until I bought this one, so I was hesitant at first to set it all the way to even 80 degrees. At first, I set it to 76 degrees just to not give him a huge temperature shock (Before, the tank was around 72 degrees, which I know, not great for a betta…) I kept it on 76 for the first few hours then I turned the dial up to 79. Iâm aware that bettas need water anywhere from 76-83 degrees. The thermometer itself does a great job heating the tank, and will turn itself on & off to adjust it when needed. In the past week or so, Iâve realized that my thermometer is set to 79, and I got a digital thermometer that I stick on the outside of the tank, and it reads about 77.7 degrees. In my opinion, this is way better than having a thermometer heat it up too much and killing your fish. I have it set now to 81, and my digital thermometer reads about 79.8 and will fluctuate between 79.8 & 78.6. For me, this is perfect for my fish. If I wanted to I could probably turn it all the way up to 82 & it would set at about 79.9-81.5, but I havenât done that yet. Overall, I think this is a great heater. It definitely will not over heat your fish. The temperature settings on the thermometer range from 68-89 degrees. Iâd recommend starting off lower than what you need just to gauge how well the thermometer works in your tank. Itâs a little off, maybe about 1.5-2 degrees from what you set it, but Iâd just get a digital thermometer that sticks on the side of your tank to double-check the temperature. Iâd definitely give this heater a try!! 🙂
Raymond Quiambao –
Works as described.
I use this to heat up my water during weekly water changes. Works great.
Adam Sarnovsky –
Horrible at doing itâs only job.
Literally the worse aquarium heater I have ever owned. The day I bought it, it would only heat my 5 gallon to 70 degrees when turned the whole way up to 86. Over time (the last month and a half), it has progressively lost power. Now I have it turned up to 90 and it only heats my tank up to 67. Seriously garbage, spend the couple extra bucks and get the fluval marina mini heater.
AStrong –
This is a great heater for the price
This is a great heater for the price. I have a 5-gallon hex tank and was worried about the size of this taking up a lot of tank space for my betta, but it fits in the back nicely. The outer glass coating is also thick enough so the heat coming off of the heateris not too intense. I have heard that some heaters will only raise the temperature of the water by a few degrees above room temp, but this heater allows you to set the temperature you want the water at. In the winter, when I have my heat turned up, I can see the light on the heater turn off when the water temperature is already at the desired temperature. If I turn my apartment heat down, the light on the heater will kick back on. I do have a small thermometer attached to the side of the tank just to make sure the temperature is where I want it, and it’s usually accurate plus or minus a couple degrees.My betta seems very happy and healthy, and I’m glad I chose this heater!
Horton, M –
Heater found to fluctuate temp within about 6°-7°F, but not a bad heater
Iâve had this heater for some time now, but I donât use it for long periods of time because Iâve found that it fluctuates a bit. I watch my tank temperatures like a hawk because I keep bettas which like it at a nice toasty 78°-80°F, but this heater will be at 78° for hours and then jump up to 85° without being touched. I have checked with several aquarium thermometers before becoming absolutely certain that it was the heater, and Iâm confident that Iâm operating it correctly. The heater itself is not bad, and I may have gotten a defective one- but I still use it as an emergency heater when needed, and if you arenât afraid of a few degrees of fluctuation in temp, then this is probably a great heater option for your tank.
Yydriel –
Great little heater for up to a 5 gallon tank. Could easily heat a 10 gallon with two of these placed on opposite sides of the tank. The power draw is minimal while the heater is inactive, my hydro bill went up by less than 50 cents total for the month, and that is with adding a bio-filter on top of this heater.According to my tank thermometer, this little guy heats to within 1C of accuracy. Impressive, considering the radiators in my apartment are very inconsistent for the ambient room temp. The suction cups tend to slide around when you adjust the temp dial, but I have not yet had any issues with the heater actually falling off the tank glass.
Celia A –
This is the second heater I bought for my 3gal tank. The first one was useless. I use a separate thermometer for an accurate temp reading and the water is always within the range it’s set to. I like that you can easily change the temperature with the red knob. My betta fish loves it and can often be found snuggling up near it. I’ve had it for 5 months and it continues to work well. It’s also easy to clean.
Amazon Customer –
I love these heaters. Itâs tough to find aquarium heaters for small tanks, but these are perfect. Maintain the temperature very well.I have these in all four of my Betta tanks; setting up my fifth today.
Fiona Macelli –
This heater is only ok. I bought the 5g heater for a 2.5g mini aquarium and (unless it’s a sensing issue) it doesn’t seem to be powerful enough to keep up, resulting in a 1C temperature drop overnight. The top suction cup is already weakening also and the unit is mostly held on by the bottom one right now. I’ve had this for 3-4 months.
J.L. –
This aquarium heater is old school – no gimmicks. Bought the 25W version for a 3G nano tank – it’s accurate, adjustable and reliable.