# inline heater - before or after co2?



## df001 (Nov 13, 2007)

We picked up a Hydor ETH300 for the 65 gallon, too damn busy to make a DIY inline.

thoughts? filter -> heater -> co2 diffuser? or filter -> co2 > heater?

I'm not too worried about air going into the heater due to the way my co2 diffuser is made, that said I dont want to risk having a problem with heater melt-down.

thoughts? links to previous threads on this topic?

thx


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## cliff (Aug 30, 2010)

I'd go with option 1 personally, unless someone with experience says otherwise.


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## default (May 28, 2011)

i would place the co2 last, since co2 is suppose to cause wear on equipment more quickly, i would just play it safer with it at the end and not have to past through something else.


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## df001 (Nov 13, 2007)

Yeah i thik thAts what i'll do, filter, heater, co2 just incase we power out or the solenoid fails etc etc i wouldnt want it to die...


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## Mr. Scruples (Apr 20, 2012)

The inside diameter of these Hydor heaters is bigger than the diameter of the inlet/outlet nipples (it's like a chamber in there, rather than a straight pass-through), so you really want to try to minimize the possibility of any kind of bubble getting trapped inside.

I have mine immediately after the filter stage, but I've noticed that after I clean the filter it helps to knock on the side of the heater a few times because there are often a few trapped bubbles in there from when the filter starts up again..

I would definitely go with option 1: filter --> heater --> cO2


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## df001 (Nov 13, 2007)

Realized the 2217 outflow is 12mm, the 300w is 16mm, swapped it out with a 200w 12mm, hopefully shouldnt be an issue, tank is running near 80 with a 100w anyway so it should be ok


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## Tovarish (Nov 10, 2011)

I used to have 200W on 35 gallon, now got 300W on a 90 gallon tank, truth be said, I suspect ETH200 would be enough for 90 gallon 79 temp (these heaters are way more efficient than classic ones)

Connected mine on a closed loop after the co2: 
Mounted heater after pump, before the co2 reactor but co2 is looped back via purge valve on the AM1000 to the pump intake. 
As the heater is close to being vertical I am not worried of any gas buildup at all.

Oh, and I used to have ETH300 connected to the outflow of 2217: placed hoses in boiling water in order to get those on to the 5/8" connectors.


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