There are basically 3 options when it comes to heaters"
1. In or on the tank.
2. In a filter.
3. Inline external.
Now, lets consider what sort of tanks and equipment is mostly used by hobbyists and why.
1. Most folks have one tank and they usually end up with a hang on filter and an in tank heaters.
2. Some folks get hang-ons with the heater inside the filter. Something I consider a poor concept.
3. Canister filters cost more than other types of filters so are nowhere near as popular as cheaper options. Some canisters have built in heaters. Again a poor concept imo.
4. Inline heaters must have a method of circulating tank water through them. Most often this is done in concert with a canister. However, it is possible to power an incline heater wusing a pump or powerhead. I cannot imagine why one would choose this method.
Yhe above said I can report that I have 3 canister running. All three have Hydor inline heaters. One of these heaters had been on the same canister now for about 20 years before I had to replace it. This is superb performance compared to the other options I have used. I have had two heater failures where the heater got stuck full on and wiped out a lot of fish very fast. The Hydor that failed stopped working and no fish died. I even have a Hydor NIB on the shelf as a backup. I used to have 2 but I used one
I can also say that in my 150 gal. I have an in tank heater in addition to the one on the canister. But that filter is too small by itself to keep that tank warm enough. The canister is also not sufficient for that size tank and there is an AquaClear 110 and an old H.O.T. Magnum also filtering the tank.
Imo the only reliable heaters I have owned, and I have tried a lot of different brands, are my inline Hydors. In the old days the Ebo-Jaegers were good heaters. I had one run great for 20+ years. But that is very rare for any in tank heaters to last these days. Ebo was bought out years ago.
Fortunately, I discovered heater controllers and to date they have never failed me. They only protect against an overheat, not against a total failure of the heater. I do not use them with my inlines, but I do have them in use with a lot of my in tank heaters especially for my most expensive fish.
p.s. Having just read Wills post I would add this. I was taught early on in my hobby years by a gent with over 50 years in the business and the hobby. He hated hoses on tanks and he taught me always to use hose clamps. I use them on every single hose connection involving water. So, with a canister filter and inline heating is use 6 hose clamps. One each in the in and out hoses at the canister, The another clamp on the intake and the spraybar hose connections, Finally, both ends of the inline heater are clamped as well.
I also use plastic style clamps on air lines. I do not use them on the individual air lines that go into the tank, but I use them on the bigger hoses where I have central air. So there are clamps on the main feed hoses where they come out of the air prump and then where they enter the manifolds. If the output gets split, both parts get the clamps.
