I've tried to keep Betta fish on and off for several years. The main reason I have trouble is quite simply the lack of a good tank heater. I've always only spent around $10 for one, and the last time I think I got one for around $15, and all of those little unregulated heaters only got me a temp. of about 5-8 degrees higher than the temp. in the surrounding room. Once winter set in, the Bettas all died. So this time I thought I would go for the gold and buy a Hydor where I could set the temperature and not worry about it, and even be able to raise the temp. to treat ich and other issues that could rear their ugly head if I had to. I am rating this Hydor 25 Watt at 3 stars because so far it is the best heater I have owned all of these years, but sadly it just cannot do what I expected it could, which is to keep a 2.6 gallon Betta tank 80 degrees. It can manage 78 degrees, which is good, but I feel it struggles to do that and at night the temp falls to 74 degrees, which is just on the edge of Betta cold water tolerance. Some extra information. I live in Illinois in a house that has no insulation due to how old it is, so maybe I simply cannot own Betta fish and should stop trying. We keep the winter house temp. at about 67. At night to save on heating bills (it costs a fortune to heat our home) we drop the temp. to 63ish. The Hydor (which by the way the Hydor from the Amazon photo came to me and not the "Theo" version, whatever that means) thus provides me with a stable 11 degrees over my ambient house temp. so perhaps I am asking for a 25 watt to do too much. It can do no more than 78 regardless of the setting I dial it up to. I have the tank in the main living room area about 15 feet away from the nearest window, and it gets no outside light or drafts. I own a Fluval Spec 3 and have 4 red cherry shrimp and 1 Betta. The design of the Spec tanks is such that the filter and heating elements are hidden in the "back" compartment of the tank which is separated from the front by a partition, giving the tank a very classy look. I figured that due to this, this could be a reason for poorer performance of the Hydor heater, because being in an enclosed small space it, in theory, would heat that compartment's water temp. to the dialed-in amount, read it as the perfect temp. and then stop, without said water getting dispersed into the main body of the tank at that same temperature. I thus raised the originally set temp. from 81 to at around 88 degrees to compensate for this possibility, but it has kept only at 78 regardless. As an added assist to the heater, the filter hose back in that compartment I have cut a few small holes in to lessen the output flow from the nozzle to allow for better Betta living (not giving too strong of a current inside the tank), but this also has the added benefit of circulating the heat from the heater in that compartment better too, which should be helping the situation! When I read the bad reviews this heater got (and of most of the heaters I have researched this is the top rated and best performing) they mentioned that their main issue for the most part was that the heater fried their fish or that the heat output was simply too much! And that was for tanks larger than mine. I've never had such a problem with any heater I have ever owned so I took that as a plus for this one which actually helped sway my decision to buy it. Overheating I can handle...but this is only a 2.6 gallon tank and it just can't pull off 80 degrees. At this point I am debating going up a size to the Hydor 50 watt. but have to figure out if that will fit my tank or be too long. 25 watts doesn't seem to be enough even though it specifies in the listing that the 25 watts is for tanks sized 2-7 gallons and the 50 watts is for tanks 5 gallons and higher. I would GLADLY pay $50-75 for a heater that I could set to 80 degrees, maintain that temp. well without going over, and also be able to raise it 5 degrees higher and lower as desired...one that works the way you imagine it should work. If someone knows of any heater that can do this, please tell me. I really love Bettas and I really want to keep one and not have it die come winter time. How do people even own fish in colder states than mine? I've included photos that show the interior rear compartment set up with the Hydor dial set to 88, and the tank temperature thermometer reading 78, as well as photos of the tank itself so you can see the scale. When I keep the stock LED lights on, I can get the tank to 79 and sometimes even 80 degrees, but I do not have the light on all day, only in the evenings when it's needed, or for taking photos. The temp. drops back as soon as I turn the lights off.