>One small caveat is that such cables are in fact 120 volt units, and
>having high voltage drops ACROSS your tank is a potential disaster if the
>insulation should wear thin at opposite ends of the tank. 

It shouldn't do the fish or plants any harm, as long as the conductivity in 
the tank isn't too high, and I don't think that in a freshwater aqarium you
get levels near the level to become dangerous. Putting your hand into the
water on the other hand will give you a bit of a tingle, or as much as a 
bit of a joult. 

Adding a stainless steel ground probe to the water will greatly help, with
a thick (5mm) copper stranded wire connected to the earth pin of a 
power outlet.

Electrocusion BTW, is not the result of the voltage potential in the water,
but rather the quantity of the current that ends up flowing through your
body. The factors the contribute to this do depend in part to the voltage
drop, but also to the quantity of electolytes in your bloodstream, the 
conductivity of your skin, and how well part of your body is grounded.

If you are standing on a wet metal floor that is grounded and reach into
a tank that is live, you will probably know about it real quick. But then
again if you reach into a live tank with leather shoes that are pretty 
dry and your skin isn't too conductive, you will probably only feel a

I am not condoning using live circuits exposed to water, and definately
suggest that every aquatic gardener and aquarist install earth leakage
protection and/or core balanced circuit breakers for their own protection.
Fitting protection to ALL the circuits that feed your fish room/tanks is

I have had a heater go leaky on me and measured the potential of the 
water to be 185VAC above ground we have (240VAC), and been given
a rather good tickle, so I suppose a person with a lower resistance 
might have got a much higher joult than me.

Marque  APD - ANGFA(NSW)