urchin electrical hazard

[eleodes]

i just had a frightening surprise.

i was inspecting a tank that we have in a CLASSROOM here that contains some <em>Lytechinus variegatus</em> 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.

 

[JR719]

That would not be the first GFCI to not work. I've had one that would not trip even when I deliberately messed with it. Don't know why, guess they don't do Quality Control.

 

[eleodes]

i wonder what i should do about this. like i said i have it in a classroom. is this system safe?

maybe i should just make a policy that all of the power needs to be off before people work in the water.

i am guessing that the urchins were not electrocuted, but rather were poisoned by either copper or ozone coming from that wire. i noticed that there were some other smaller creatures in there that were still alive.

 

[eleodes]

is there any way to test GFCI's other than just using the test button that they have between the outlets? additionally, would it be expected to trip if just one of the two wires were bare?

 

[JR719]

Not really sure about testing. I had a cut extension cord. I plugged it in and touched the wires together, should trip right? Well, the breaker tripped but the outlet did not. Was and still not very impressed with them. I am guessing the urchins were electrocuted. Just as though a heater broke, zap everything. As far as testing, not sure. I would like to know though. Thought touching the 2 wires would do it.

 

[eleodes]

i just tested and got measurable copper from the water- .25mg/l. i suppose that i should toss out the sand and rock that was in there too because now it's poisoned with copper. at the spot where they had exposed the wire a lot of it had been eaten through by whatever electrical reaction was happening.

i think that i am going to make a new rule that everything needs to be turned off before anybody reaches into tanks.

i'm certainly not going to keep any more of those urchins: they're all dead anyway.

 

[JR719]

If you show copper in the tank, get rid of it all. I would say good luck though. Sorry for your loss, prob not a bad idea to turn off before putting the 'ol hands in. Don't need the liability, you might want to add a ground wire to the tank.

 

[eleodes]

it's not a big deal. although those urchins were handy for talking about echinoderms in the classroom. when i got those urchins i noticed that they had some kind of good-sized annelid worm living as a commensal between the spines right around their mouths. interestingly, i found a couple of the worms still alive underneath the dead urchins. i am going to keep them and try to get some pictures of them tomorrow.

would a ground wire make it any more safe? i had understood that those were mostly for reducing the negative effects of stray voltage on fish.

 

[Wiskey]

your gfi is far more likely to trip in a situation like this if the tank is grounded by a ground probe.

GFI's won't trip for a dead short (extention cord experiment), that is not their job, they only trip when power is leaking to ground. gfi=ground fault interuptor

whiskey