Aquarium Heaters by Fluval. Details:Keep your small aquarium at the perfect temperature with the P25 Submersible Aquarium Heater. This 25W heater is pre-set to 76-78°F (24-26°C) for effortless, worry-free use in nano aquariums. Built with a shatterproof polymer exterior, it ensures safety and durability for both freshwater and saltwater tanks up to 6 gallons (25L). Its fully submersible, waterproof design allows flexible placement, while the LED indicator shows when it's actively heating.
Aquarium Heaters by Fluval. Details:Keep your small aquarium at the perfect temperature with the P25 Submersible Aquarium Heater. This 25W heater is pre-set to 76-78°F (24-26°C) for effortless, worry-free use in nano aquariums. Built with a shatterproof polymer exterior, it ensures safety and durability for both freshwater and saltwater tanks up to 6 gallons (25L). Its fully submersible, waterproof design allows flexible placement, while the LED indicator shows when it's actively heating.
in 7 offers
last seen 15 May 2026
The lowest price we last saw for Fluval P25 Submersible Aquarium Heater for Up to 6 Gallons, 25 Watts was $30.32 at The Vet Shed, compared across 6 retailers (last seen 15 May 2026). Prices may have changed since.
The all-time low we recorded was $29.41 on 27 Dec 2025.
Prices last updated 15 May 2026.
Fluval P25 Submersible Aquarium Heater for Up to 6 Gallons, 25 Watts
Aquarium Heaters by Fluval. Details:Keep your small aquarium at the perfect temperature with the P25 Submersible Aquarium Heater. This 25W heater is pre-set to 76-78°F (24-26°C) for effortless, worry-free use in nano aquariums. Built with a shatterproof polymer exterior, it ensures safety and durability for both freshwater and saltwater tanks up to 6 gallons (25L). Its fully submersible, waterproof design allows flexible placement, while the LED indicator shows when it's actively heating.
Aquarium Heaters by Fluval. Details:Keep your small aquarium at the perfect temperature with the P25 Submersible Aquarium Heater. This 25W heater is pre-set to 76-78°F (24-26°C) for effortless, worry-free use in nano aquariums. Built with a shatterproof polymer exterior, it ensures safety and durability for both freshwater and saltwater tanks up to 6 gallons (25L). Its fully submersible, waterproof design allows flexible placement, while the LED indicator shows when it's actively heating.
Last updated at 15/05/2026 18:41:52
Fluval Pre Set Aquarium Heater PS25 - 25 watt
30-day returns
Fluval Pre Set Aquarium Heater 25w P25
Delivery $15
Fluval Pre Set Aquarium Heater 25w P25
Delivery $9.99
Fluval P Submersible Aquarium Heater - 10W 25W
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval P25 Submersible Pre-Set Heater 25W (A744)
Delivery between 21–29 May $8.95
Fluval P25 Pre-Set Aquarium Heater
Delivery between 20–24 May $15.52
originally posted on aquariumcoop.com
I think this is a nice little heater. I’m giving it only 3 stars because it did not even begin to heat my 6 gal long bookshelf tank. I kept questioning the employee, who repeated that it should be all I needed - and the specs DO match the tank volume. The length though, combined with a low flow sponge filter, made me concerned it wouldn’t be enough. But after a few days trial, I finally installed another 25 watt at the opposite end, and now have temps around 80 degrees (perfect for a betta)! It works fine - just keep in mind the configuration of your set up.
originally posted on petco.com
You can't submerge it and if that is okay this is a great heater. I have a 10 gallon rimless Lifegard crystal tank. Its stands just over 11 inches tall. With the water at about 1 inch below the rim the fluval drops into the back filter and sticks up above the rim by about 1/4 inch. This provide easy access to the temperature adjustment knob.I've adjusted the temperature to where I want it (read below) and I've checked my temperature every day and it is holding steady now.The heater has had no issue bringing my 10gallon tank up to temperature and maintaining. I started with room temperature water at about 65F and gradually brought it up to 79 degrees. I used a cooking probe thermometer to check the temperature. I do not and would never recommend trusting the dial ... MoreYou can't submerge it and if that is okay this is a great heater. I have a 10 gallon rimless Lifegard crystal tank. Its stands just over 11 inches tall. With the water at about 1 inch below the rim the fluval drops into the back filter and sticks up above the rim by about 1/4 inch. This provide easy access to the temperature adjustment knob.I've adjusted the temperature to where I want it (read below) and I've checked my temperature every day and it is holding steady now.The heater has had no issue bringing my 10gallon tank up to temperature and maintaining. I started with room temperature water at about 65F and gradually brought it up to 79 degrees. I used a cooking probe thermometer to check the temperature. I do not and would never recommend trusting the dial on any tank heater. I kept adjusting the knob until the tank reached 79. Then I would back off one click. As the knob is turned, one feels a click. I noticed the temperature was not stepping down incrementally and I wanted to bring my tank down to around 76 to 77 degrees. I turned the knob multiple clicks and then brought it back up one click at a time. Bottom line, don't assume each click is a uniform step up or uniform step down in temperature. Always validate your temperature with an accurate thermometer.The compartment where the heater is located in the back of the tank also contains a media bag and media. I was concerned at first at the amount of heat coming off the heater. While the heater is on I can't my finger there a significant amount of heat coming off the heater. That is, I didn't want a hot heater melting my media bags and cooking my bacteria. There is no evidence of overheating. Of course, never let the water level drop or the 50watts of head will cause damage. Stop your heater when performing water changed.
originally posted on aquariumcoop.com
When heating Nano tanks, it can be difficult to find heaters that work properly....especially ones that have a preset thermostat!I'm currently heating a 3 gallon acrylic tank and a 5 gallon Fluval Spec with these heaters.I'm very happy with the performance, safety and sleek design this aquarium heater offers!! It is been very safe and will not burn fins, shrimp and snails!! I can highly recommend it!! It's also a great value! I'm very pleased with this heater all the way around!!!
| Product dimensions | 15 x 7 x 3 cm; 192 Grams |
| Language | English |
Fluval Pre Set Aquarium Heater PS25 - 25 watt
30-day returns
Fluval Pre Set Aquarium Heater 25w P25
Delivery $15
Fluval Pre Set Aquarium Heater 25w P25
Delivery $9.99
Fluval P Submersible Aquarium Heater - 10W 25W
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval P25 Submersible Pre-Set Heater 25W (A744)
Delivery between 21–29 May $8.95
I think this is a nice little heater. I’m giving it only 3 stars because it did not even begin to heat my 6 gal long bookshelf tank. I kept questioning the employee, who repeated that it should be all I needed - and the specs DO match the tank volume. The length though, combined with a low flow sponge filter, made me concerned it wouldn’t be enough. But after a few days trial, I finally installed another 25 watt at the opposite end, and now have temps around 80 degrees (perfect for a betta)! It works fine - just keep in mind the configuration of your set up.
You can't submerge it and if that is okay this is a great heater. I have a 10 gallon rimless Lifegard crystal tank. Its stands just over 11 inches tall. With the water at about 1 inch below the rim the fluval drops into the back filter and sticks up above the rim by about 1/4 inch. This provide easy access to the temperature adjustment knob.I've adjusted the temperature to where I want it (read below) and I've checked my temperature every day and it is holding steady now.The heater has had no issue bringing my 10gallon tank up to temperature and maintaining. I started with room temperature water at about 65F and gradually brought it up to 79 degrees. I used a cooking probe thermometer to check the temperature. I do not and would never recommend trusting the dial ... MoreYou can't submerge it and if that is okay this is a great heater. I have a 10 gallon rimless Lifegard crystal tank. Its stands just over 11 inches tall. With the water at about 1 inch below the rim the fluval drops into the back filter and sticks up above the rim by about 1/4 inch. This provide easy access to the temperature adjustment knob.I've adjusted the temperature to where I want it (read below) and I've checked my temperature every day and it is holding steady now.The heater has had no issue bringing my 10gallon tank up to temperature and maintaining. I started with room temperature water at about 65F and gradually brought it up to 79 degrees. I used a cooking probe thermometer to check the temperature. I do not and would never recommend trusting the dial on any tank heater. I kept adjusting the knob until the tank reached 79. Then I would back off one click. As the knob is turned, one feels a click. I noticed the temperature was not stepping down incrementally and I wanted to bring my tank down to around 76 to 77 degrees. I turned the knob multiple clicks and then brought it back up one click at a time. Bottom line, don't assume each click is a uniform step up or uniform step down in temperature. Always validate your temperature with an accurate thermometer.The compartment where the heater is located in the back of the tank also contains a media bag and media. I was concerned at first at the amount of heat coming off the heater. While the heater is on I can't my finger there a significant amount of heat coming off the heater. That is, I didn't want a hot heater melting my media bags and cooking my bacteria. There is no evidence of overheating. Of course, never let the water level drop or the 50watts of head will cause damage. Stop your heater when performing water changed.
When heating Nano tanks, it can be difficult to find heaters that work properly....especially ones that have a preset thermostat!I'm currently heating a 3 gallon acrylic tank and a 5 gallon Fluval Spec with these heaters.I'm very happy with the performance, safety and sleek design this aquarium heater offers!! It is been very safe and will not burn fins, shrimp and snails!! I can highly recommend it!! It's also a great value! I'm very pleased with this heater all the way around!!!
So far so good with this heater. Seems pretty comparable to an Eheim 50W I also have with one thing that’s better and one thing that’s worse.Pro: the cord is thinner and easier to manipulate behind the tank/cabinet than my Eheim.Con: while the temperature setting is adjustable, the increments are not as precise as an Eheim heater.
I got this heater for my office 5 gallon. The building/office is extra cold during the winter, so I went one size up. I like that this model has an indicator light showing when it's on and heating. A couple weeks in and the temperature is still perfect.
Worked fine for 1 week and then I noticed the blue led inside the heater was remaining on for longer periods of time. I did not change the temperature dial, it was at 78 since I bought it. I also made sure that the water level remained above the line. Stopped working after 10 days.
I had a Marina C25 (the Co-Op's previously stocked heater) that was looking ugly partly due to some very old nerite eggs that are impossible to pick off. I bought this to freshen up the look, and it can barely heat my 4.4 Gallon above ambient. I have an external temperature control set to 74-75 and this heater never turned off after 2 weeks. The best it ever did was 73.5, 3 degrees over ambient. While that might seem good enough, I doubt it could handle heating the tank after water changes. I ordered another Marina C25 from elsewhere since the Co-Op doesn't carry them anymore. With the same location next to the filter, same settings on the external heater control, it hit 74 within the hour. *disgruntled Cory voice* The old one was better!
I ordered this for my 5 gallon tank that houses my Betta, two mystery snails, and some ghost shrimp. Unfortunately, the item I received heated my tank to 82 degrees. I contacted customer service and they were very quick to respond. It sounds like the item I received was just calibrated incorrectly, but they sent out a replacement immediately and that heater is working great and maintaining my tank at 79-80 degrees. Great product and amazing customer service!
I ordered this for a 5 gal quarantine tank, and eventually for a 2.5 gal shrimp/snail tank. I was very excited to find a nano tank preset heater, as the flat heaters I had from aqueon remain on and are not enough for the winter (even with two, one of them being a size larger) even in a 1-2 gallon tub, and are too much at other times Of year (brought my 2.5 gal up past 82 degrees, despite the room never getting past the low 70s). So this was meant to be a dream come true, but I went to check the temperature before writing this, and it was 80-81 degrees, and the heater light was on, and it is in the line of my filter output. So I’m not so sure of this product anymore, but it should at least be better in winter.
this is a good heater but it won't work for the thing Cory advocates about using lower wattage than the usual recommendation per size of your tank. I tried using it in my 10gal betta tank and poor Hulagu was freezing because the water stayed at 74-75F. Moved it over to the 5.3gal right next to the 10gal and that tank was getting nice and toasty, right up there around 76-78 as advertised. Thus, my opinion is to use this heater as it's intended and not try to go "off label" like I did. Only other thing I'd mention is that, as I've noticed with other Fluval products, the suction cups blow.
| Product dimensions | 15 x 7 x 3 cm; 192 Grams |
| Language | English |
