aqueon 300w submersible heater - knocking noise - slight condensation

time to toss it?

i have an aqueon submersible heater in a 55gal tank (tank is only filled halfway at the moment)
-heater is rated for 75-90gal... should it not be in here?
-also im in northern california where winter temp is usually 40-70F

theres also slight condensation inside the glass tube
tube is laying sideways with the top elevated slightly higher than the bottom.
most the condensation is near the top but theres also a bit near the rubber stopper at the bottom

temperature is holding steady at 78F





*just wondering, do these have potential for failure like the stealth-pro's? as seen in this thread:
http://www.plantedtank.net/forums/equipment/103155-beware-marineland-stealth-pro-heater-12.html

**** **** ****

I have 3 of this same heater
and it is heater #2 that i made this thread about....

a few months ago i retired heater #1 becuase it was making the knocking noise (although I never checked for condensation)
I replaced it with heater #2 in and was still having the knocking problem... but the knocking stopped when I redid my electrical stuff. I previously had both heater #1 and then heater #2 plugged into a surge protector which was plugged into another surge protector which was plugged into the wall. I redid my wiring so it was only plugged into a single surge protector, and the knocking stopped. I ran it like that for a while

well i moved the tank to my parents house where I had it running half full for about a week. today I unplugged everything (from a single surge protector plugged into the wall) and drained most the water so I could shim/level out my tank. when i started refilling the tank (heater below water line) heater #2 started making a knocking noise and slight condensation was present. so I made this thread.

so there was knocking and condensation so I unplugged #2 and replaced it with heater #1. once again the knocking continued and condensation was quickly visible

so right now I just removed heater #1 and installed heater #3 and while I have yet to spot any condensation, the knocking is once again present...

this is also my first time using heater #3, it is brand new



WTF????


*edit*
theres now a slight spot of condensation around the top of the coil and a lot of bubbling occuring by 1 of the suction cup holder things but not the other one

*also, could lack of ciruclation also be a problem?? I currently have my filter off, due to a problem with the impeller
*repositioning (shifting side to side along the suction cup holders) also temporarily stops the knocking

the knocking stopped