urchin electrical hazard

[eleodes]

(note: i cross-posted this thread in "Reef Discussion". i am strongly interested in feedback)

i just had a frightening surprise.

i was inspecting a tank that we have in a CLASSROOM here that contains some Lytechinus variegatus urchins. it was making a funny noise and i noticed that the hang-on filter was not moving any water. an inspection of the filter revealed that the urchins had chewed through the power chord, which was producing some kind of gas bubble and the rattling sound. the brand new GFCI that it was plugged into DID NOT TRIP and all of the urchins were on the bottom of the tank and dead.

i'm sure glad that it happened the way it did and that i didn't reach my hand into the tank.

 

[danferd2002]

how would they chew on a chord tha was outside the tank.

 

[Paul B]

Eleodes, thats why you need a ground probe in the water. With just the two wires of a powerhead or filter, light etc, the GFI will not trip in that instance, it will only trip if there is a ground somewhere in the system. If you put your hand in the water the current would pass through you (Painfully) and the GFI would happilly stay on.
Paul

 

[WY_REEFER]

What kind of hang on filter has a cord inside the tank?

The reason the GFI did not trip is because the current was going to the neutral. If you would have had a ground probe some of the current would have went to ground and the GFI would be able to measure this current and trip.

If you would have touched the water the current would most likley travel through you to ground and the GFI would have also tripped.

 

[Chckrbrd Wrasse]

Whisper In-Tank Filters have its wiring inside the tank. I am not sure if that is the type of filter used. I am just saying some hang on filters are internal not external. Nice to know about the urchins chewing through the wiring.

 

[Gudwyn]

The gas bubbles were hydrogen and oxygen.

 

[eleodes]

yep, it was a Whisper. thanks for notes about the ground probe. so is this one acceptable:

http://www.drsfostersmith.com/produ...&Ntx=mode+matchallpartial&Np=1&pc=1&N=0&Nty=1

?

 

[Paul B]

That one would work
Paul