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RE: Ballast Heat

> Date: Wed, 11 Nov 1998 14:49:40 EST
> From: TomWood3 at aol_com
> Subject: Re: Ballast Heat
> Erik Leung wrote about placing ballasts under the tank to create
> convection
> currents.  It's my understanding that the convection currents created by
> the
> heating cables are dependent on a water temperature differential across a
> very
> small area.  The heat from the ballasts are radiant heat that will tend to
> create a relatively uniform warmth across the bottom of the tank.  How
> will
> this create convection currents?
> Tom
	At the risk of being flamed (not to mention the personal attacks on
my judgement, or lack thereof) :-) I'm going to throw out my viewpoint on
this subject.

	I recently set up a new 75 gal tank and had every intention of
installing heat cables.  I went as far as creating a database to calculate
what transformer and wire I would need and I even bought everything to build
them.  I was concerned with disrupting the cables while planting and
rearranging, so I changed my mind at the last minute.

	Now, I'm not claiming to know anything about thermal dynamics or
convection currents, but I believe convection currents could only be
produced under certain conditions, and these conditions were not going to be
present in my tank.

	In order for a current to initiate in a substrate, there must be a
path for it to follow.  If only gravel were used, this path would exist.  My
setup consists of Profile Aquatic Soil with a layer of 1-2mm gravel on top,
and I'm assuming this is typical of many others, whether laterite, kitty
litter or soil is used, the consistency of the substrates should be
comparably dense, thereby leaving no paths for currents, and in effect,
forcing the entire substrate to absorb the heat.  Basically, the same thing
that Eric is proposing, and also what I set up.

	I mounted the Ballast's for my MH pendants in the cabinet, and along
with the pump and CO2 solenoid, enough heat should be created to warm the
substrate, which I think is more beneficial than pumping water through the
gravel.  It seems to me that if you have currents, nutrients may be
deposited into the substrate, but there may also be nutrients carried back
into the water column, becoming fair game for the algae (if water goes in,
water must come out somewhere else).  I believe that nutrients should be
added to the substrate and not the water column, at least as much as is

	This tank has been in operation for only two weeks, so I can't make
any claims, I'm only expressing my opinions.

	Bob Ashcraft
	Cowering, but holding my ground.