re: substrate heating

>No way.  Dupla charges $90-140 for their cables.  The one in my tank, a
>50-watter, makes about two full trips back and forth, making its length
>under 20 feet.  That's still half the price Dupla would charge.  The key
>is not being stronger than normal wire, the key is being more resistive!

>* Please please tell me the source for this! :) *

The company is:
     Cooner Wire
     9186 Independence
     Chatsworth, CA 91311

They sell wire they call Miniature Electrode Wire AS 155 Series which is 
stranded copper with a silicone rubber insulation.
Part #         Wire Gage ohms/foot
AS155-28  28        .066
AS155-29  29        .085
AS155-30  30        .108
AS155-31  31        .145
AS155-32  32        .170
AS155-33  33        .218
AS155-34  34        .272
AS155-36  36        .436
They also sell AS 180 Series wire which is stranded stainless steel with a 
silicone rubber insulation.
Part #         Wire Gage ohms/foot
AS180-28  28        2.8
AS180-29  29        3.57
AS180-30  30        4.56
AS180-31  31        6.13
AS180-32  32        7.18
AS180-33  33        9.19
AS180-34  34        11.48
AS180-36  36        18.38
AS180-38  38        30.63
AS180-40  40        45.94
They also sell wire they call Bioflex Insulated Wire.  It can have either 
clear non-hygroscopic fluorocarbon (FEP) or polyvinylchloride (PCV) 
insulation.  Wire sizes range from 28 - 40 gage with nominal resistance  of 
.066 to 1.08 ohms / foot for copper wire or 2.8 - 45.94 ohms / foot for 
stainless steel wire.  It is described as being ultra flexible and suitable 
for implantation in vivo.  It is multistranded.

I looked at using wire from this company and decided it was more money  than 
I  wanted to spend so I used standard stranded 26 gage copper wire in my 
tank.  I also ran two lengths of wire and brought all four ends out of the 
tank.  Now if one wire is broken I will attach my transformer to the other 
wire.  This seemed a good safety measure to prevent having to tear down a