From: jason@lanai.cs.ucla.edu (Jason Rosenberg)
Subject: Re: Induced voltages
Organization: UCLA, Computer Science Department
Date: Wed, 18 Nov 92 17:50:01 GMT

Carlos Eberhardt <eber0005@student.tc.umn.edu> writes:

>	I recently read in a response to a post that induced voltages are
>believed to be the cause of hole-in -the-head. I am assuming that these
>voltages are caused by the electric motors in powerheads and power
>filters (by the coils used to drive the motors?). 
>Is this a good assumption? 

Yes, most people have measured between 70-120 Volts AC, at 60Hz (the frequency
of wall outlets).

>If so, then what is the theory behind grounding a tank? 

You put a grounding probe in the tank water, and connect a wire to it to
the ground screw on your wall outlet (make sure your wall outlet is properly
grounded, many older houses don't have properly grounded outlets).  The
probe then bleeds off the voltage by conducting a very miniscule amount
of current to ground.  The tank water should drop to or near 0VAC.  The
probe must be a good conductor, and be non-corrosive.  The only commercially
available one I've seen is made of titanium.

I don't completely understand the mechanism which causes hole-in-the-head.
However, it appears to caused by some sort of infection (bacterial? parasite?).
But it appears that the induced voltages cause the fish's resistance to
such infections to be weakened.  The head and lateral line of many fish
serve as sensor organs for detecting very minor fluctuations in ambient
electromagnetic potential.  They become over-whelmed when in the artificial 
aquarium environment.  These organs become overly stessed and the resistance
to disease decreases.  Be advised, however, that I am mostly aware of
the issues relative to Marine aquaria.

Below, I've included the text of a message I sent to another fellow netter.
I've answered some of the other question you may there.  I am very interested
in this approach, and would like to hear more about other's experiences with
grounding their tanks.  Especially, it would be good to hear from freshwater
experimenters out there.  Personally, it has worked well for my striped
damsels....

Jason


****


Don't ever expect your local fish stores to ever have any clue about
equipment.  You can mail order it.  Check ads in FAMA (Freshwater and Marine
Aquarium Magazine).  If you don't have an issue, write back and I'll send
you the address/phone numbers of some of the locations.  Should be around
$30.  

The problem with making them is that it must be a good conductor, but be non-
corrosive in salt water.  Solution Ground is made out of titanium.  It's just
a probe in a plastic sheath, with a small titanium tip exposed.  You then
connect the wire to the ground screw on your wall outlet.  Apparently, there
are grades of stainless steel that are supposed to be non-corrosive, but I'd
be very careful with it!  You want the probe to be as small as possible and
still be functional.  Also, if you have access to an AC voltmeter, it might
be a good idea to measure the induced potential in your tank to see if there
is a problem.  Then if you ground it, you can see that it is working.

I really think your better off just buying the darn thing.  Unless you have
a free source of titanium.

The evidence that it works is based both on magazine articles and netter's 
experience.  Several people have reported good results with it.  Some people 
find that it doesn't always cure HLLE (Head and Lateral Line Erosion), but it 
definitely stops its progress and new cases don't usually crop up.  There was
an article in Marine Fish Monthly (I didn't see it myself) which did a study
with blue tangs (the most notoriously susceptible fish to HLLE).  They had
a tank full of blue tangs, with a grounding probe.  They left it in for
a few weeks, the fish were fine.  They took it out for a few weeks, the fish
started fading around the head.  They put it back for a few weeks, the fish
healed.  They took it out, the fish relapsed....It seemed pretty convincing
to me (and I only heard about the article....).  It has worked with my
damsels almost completely....

Jason








>(I guess this may be more of a question for an
>electrical engineer, but aquarium folks often end up being biology smart,
>so why not eletrical?).
>	Also, is there a way to build your own grounding device? I've heard one
>can be bought for about $30, but if I can build one cheaper, I'd like to.
>	Responses directly to me are preferred, but if this topic seems
>interesting enough, you may want to post to the board.
>	Thanks in advance for any responses!

>Carlos Eberhardt    -------->  eber0005@student.tc.umn.edu
-- 
Jason Rosenberg                           Computer Science Department
jason@cs.ucla.edu                         University of California
{uunet,rutgers,ucbvax}!ucla-cs!jason      Los Angeles, CA  90024
Newsgroups: rec.aquaria