I have heard this... I guess it would help with water flow, ensuring that water is flowing over the heater and being distributed to the rest of the aquarium. If there are heat distribution issues (i.e. different parts of tank are different temperatures) it could help. If there is an overall deficit of heat, probably better to get a stronger heater, or a second heater - doubling heaters is supposed to be safer than getting a stronger one.
i will be getting another heater when money isnt so tight but i have always been curious if i ut a heater near the intake if when the water comes through the filter will it be warmer to help distribute the heat its been nagging at my mnd for months and have treid too search online to find a hypothesis but have come up with nothing its as if its probably a common knowledge bu id rally like hard evidence if this makes me sound like a noob so be it hahaha
but its just nagging nd i hate nagging thoughts they drive me a little insane bahahahaha
so if anyone can clarify a hard answer for me that would be really apppreaciative or if they have tested the theory i would love too know the outcomes and results
My guess is it does (if you do not have a strong circulation in your tank).
Since it is near the filter in or outlet there for sure will be more water displacement compared to elsewhere in the tank.
That in turn will help to ditribute the heat more efficient Instead of having a very local hot spot in the tank in case of almost no water circulation).
if there is a strong circulation caused by the filter this will not matter that much,
but when you have a very slow circulation this seems to be more efficient to me.
The orriginal filter of my main tank (use a cannister now) had a 150W removable heather inside the filter housing (intake section)
I also have a spare heather (that original one that came with the tank) and bought a better one a bit later to use in the tank.
The original one i keep as backup (Same for the filter), also use the heather it when i set up a QT
(in this case a large transparent plastic bucket that once kept fish food for when we had a koi pond)
i also have a small 5.5gallon betta tank with a very compact HOB filter that does not generate a strong circulation (Betta's do not like that). So there i also placed the heather underneath the outlet.
One of the most stable and uniform ways to achieve highly accurate and stable temperatures is with a "stirred water bath".
Fancy incubators for culturing bacteria are often of this design.
As long as your aquarium has adequate water movement, the temperatures should be quite uniform throughout.
But the more water circulation, the more even the temperatures will be. And placing the heater in an area of strong current will help disperse its heat and keep its thermostat well coupled to the average water temperature. This will improve accuracy.
But, again, as long as you have adequate water circulation in the aquarium, you shouldn't need to go to any special lengths to get very good uniformity of temperature throughout the aquarium.
Water is a fantastic heat transfer medium. It has high specific heat and excellent thermal conductivity.
thought as much this was just a nagging thought in my mind hahah dont know why but just wanted to know my filter is in a great place for circulation now with my new filter i fear it may be too powerful but it seems to be fine and shoulf be but as i only installed it today i ill be able to tell by tomorrow if my babies are strugglingwith the new current and if i have too turn it down or anything