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Re: More DIY substrate heating cable questions

In message "Re: More DIY substrate heating cable questions", Jay Bickford writes:

>The responses, however,  have brought another question to mind.  In the above
>mentioned article, the authors use an AC transformer, but Brent Harsh suggested
>the use of an inexpensive DC battery charger like found at "WalsMart" for
>charging car batteries.  Does it make a difference if you use AC or DC?  Any
>electrical engineer types want to explain the advantages and disadvantages of one
>verses the other?  Are there any concerns about efficiency?  Is one type, AC or
>DC, more electrically efficient than the other?

Hi Jay,

Just an update on my heating cables using the battery charger.
They've been running constantly since February, and I have noticed
that the charger is making a bit more noise now that it did before.
In fact, it buzzes louder than the magnum canister filter on my tank!
Since it's a bedroom tank, I'm considering changing it (or at least
re-doing it's case myself to make it more solid).  It has been doing a 
fine job of keeping the substrate about 2 to 4 degrees warmer than the 
rest of the tank (found by shoving my brewing thermometer down into
the substrate).  I can't comment on the efficiency, but judging from
how warm the charger gets, I'm sure it's not very good (but my
ballasts on the lighting are worse <grin> - someone should invent a
way to mount the ballasts in the substrate as heaters!).  Now that
it's summertime, I may have to start putting it on a timer to keep the 
tank below 90!  (I usually keep it at 86 for the discus, and the
substrate temps vary between 88 and 90 the few times I've checked -
your tank is most likely cooler overall, so you'll probably want to
start out using a timer).

Other notes:
I really need to spend some time looking at my hardness levels to
balance them with pH and my CO2 rate.  Right now, it's all just
cobbled together and I haven't really tested anything, except to note
that my pH is off the low end of the scale on my stupid test kit (6.5) 
and my ammonia test kit still reads high despite the ridiculously low
bioload.  I've also noticed some tiny white whipping worms going around the 
tank - I've seen the discus eating them on occasion and they worry me
a bit.  Walter Wu suggested that they might be planaria, but they look
round to me; could be though, I really don't have any idea - I may
have asked about them before, but I went on vacation for the last two
weeks and just had to ignore the AP digests to catch up on work e-mail.

Okay then, that's it...