Heater inside external filter?

I personally wouldn't. I'd expect it will displace media, and possible allow water to flow through unfiltered; Not to mention potential problems with the power cord.

It would work, but I'd say it would be too risky to bother.
 
What size tank and what type of hood? I've never heard of one that wont accommodate a filter and a heater.
 
I've done it before with no problems, but its always been when I've been running an oversized filter like an AC70 or 110 on a 10-29g tank.
 
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