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Re: [AGA-Member] Too Much Heat - Substrate Heating Schedule Suggestions?

I wouldn't worry about whether the cables run much or not;
I'd only focus on the water temp.

Remember that most of the electrical energy that goes into
light bulbs is shed as heat, not light. With fluorescents
and metal halide bulbs, the rule of thumb is about 65% of
inout energy is shed as heat. So your lighting is, in
effect a 75 watt radiant heater.

As far as heaters go, unless you need to add heat to the
aquarium all the time, the safest thing, in terms of
maintaining a desired water temp, is to use a thermostat.
Unless the room temp is relatively low, the heater (whether
substrate cable or other) might not run at all or very
rarely and only when the lights are off or the lighting
level is low.

An example: I used cables on a large aqaurium with a high
level of lighting. The heater only ran occassionally and
then only during about 4 months of the year. In this case,
heating was needed only when the room temp was below 70F,
which only happens during the colder months when the house
thermostat is set to 68F.

Running some of the lights for a shorter period than the
rest, as you are doing, in one way to lower heat input.

You might consider dropping down from 55w bulbs to 36w
bulbs. This would still be plenty of light and if your
ballasts "self-adjusts" or can be wired for 36w bulbs (like
a Fulham Workhorse 3, for example), then you will be
substantially lowering heat input and the diff might be
enough that a heater is needed to maintain water temps. But
36w bulbs can often be run on the same ballast and wiring
as a 55w, slightly overdriving the bulbs but still using
less energy (and creating less heat) than 55w bulbs on the
same ballast.

More air flow over the bulbs is the best way to passively
reduce heat input into the tank. Short of cutting more
vents into your hood, raising your lights a few inches
above the tank can help let some of the heat from the lamps
escape before it gets into the tank -- and this is easy
enough to try and doesn't cost any money or invovle much
work to try, at least with conventional hoods. Installing a
fan can help; sometimes a room fan pointed at the hood is
enough depending on the particular situation, including
room temp. 

Btw, if you are not especially fond of the coloring you get
with the actinic lighting, you can swap out those 50/50
bulbs for ones with a broader spectrum. You don't need
actinics to grow plants; broad spectrum bulbs work just

Substrate cables are a relatively efficient means for
heating an aquarium if the water currents are not very
strong, taking advantage of convection in the water column
to spread the heat. If the water current is strong, there
will be little convection and substrate versus sump heating
vs heating directly in the water column won't make much

Plants don't seem to care how the heat gets into the

Good luck, good fun,
Scott H.
--- Kirsten Klinghammer <klingham@pacbell.net> wrote:

> Greetings, Everyone,
> I'm a new AGA member, and I'm getting back into aquaria
> after not having any
> tanks for over 20 years.  I love plants and have set up a
> new aquarium
> (specifics below) with a substrate heating cable, which
> sounds like a great
> idea.  What I neglected to take into account is that
> lighting has changed
> greatly in the past two decades, and the wonderfully
> bright compact
> fluorescents I have now put out so much heat that it's
> them or the heating
> cables as far as heating the tank goes.  I'm trying to
> figure out the best
> way to handle this, and I'm hoping one of you out there
> can provide me with
> some guidance.
> So, the setup:
> 38 gallon R-375 Lifetech aquarium (I found a picture
> online, although ours
> is silver:
> http://www.aqlogics.com/product.asp?ProductID=6882) 
> two 55 watt 50/50 Actinic/10K Jebo compact fluorescent
> bulbs [the ballast
> needed to be replaced right away, so we put in a good
> quality one, and wired
> the bulbs so that one or both can be on]
> R-375 submersed aquarium pump, which sends water to a
> wet/dry filter (with
> filter floss and ceramic beads/stones) in the aquarium
> hood; the water
> returns to the tank from the other end of the hood; there
> is also a bypass
> flow with a venturi valve which I have opened on full for
> aeration
> Dupla Thermik 40 watt substrate heating cable, plugged
> into a Timex heavy
> duty timer which can be set by the hour
> Eheim Jaeger 150 watt submersible heater set to a lower
> temperature (for
> backup, if needed - and I don't think I'll need it!)
> Substrate (total substrate depth, 4 - 4 1/2 inches):
>   Layer 1:  1/2 - 3/4" gravel beneath heating cables (~10
> kg unwashed
> flourite)
>   Layer 2: ~2 kg FertiPlant laterite, ~8 kg FertiPlant
> Plus, and ~4 kg
> unwashed flourite mixed in aquarium by hand
>   Layer 3:  14 kg red flourite, washed to remove
> substantial amount of dust
> Just added:  A yeast reactor for CO2 with airline tubing
> leading to a
> fine-bubbling airstone in the tank (following Tarah
> Nyberg's yeast recipe on
> page 26 of The Aquatic Gardner (volume 17, number 2) [I
> bought back issues
> of Planted Aquaria and TAG - I've been learning so
> much!])
> The room with the aquarium is kept in the mid to high
> 60's (Fahrenheit)
> during the day, and about 70-71 at night.  The tank is
> not close to a
> window, so it doesn't receive any direct sunlight.  My
> goal is to keep the
> tank at about 79 degrees.  
> On to the obvious: TOO MUCH HEAT!  
> The aquarium hood, although sleek and beautiful, has few
> outlets of any sort
> - just two holes about 1 by 2 inches for tubing and wires
> to exit the
> aquarium, and some ventilation slits above the sealed
> light fixtures.  I
> find this appealing because it's attractive and it will
> keep escape-artist
> crustaceans from taking off, but obviously this gives me
> a problem with heat
> dissipation.  My husband and I are trying to figure out
> how and whether to
> mount a small fan in the hood above the lights to draw
> heat out - I'm sure
> we'll figure out something, but it'll be a little while
> before we get this
> all straightened out.  
> In the meantime, I've been turning on one light in the
> morning, about two
> hours later turning on the second light as well, then
> turning off the second
> light in the evening (leaving one), and turning that one
> off at night.  One
> or both lights are on probably about 14 hours total per
> day (based on when
> I'd like to be able to see the plants and tank
> inhabitants - only a few
> Amano shrimp right now). 
> Current solution:
> I've been having the heating cables on during the night,
> scheduled for three
> hours on, one off, one on, one off,  two hours on, and
> off for the rest of
> the day (since the lights heat all-too-well during the
> day).  Doing this
> schedule I've been able to keep the tank between 79-81
> throughout the day
> and night.  However, I have no idea what makes the most
> sense in terms of
> the heating cable schedule - should I try for every other
> hour being on
> during the night?  Is it a problem to use the heating
> cable only at night?
> Is it worthless to have a heating cable if it can't be
> used throughout both
> the day and the night (not as regards expense - it's
> bought and installed
> already - but in terms of usefulness)?   For those of you
> who have heating
> cables which don't have thermostats, what on/off schedule
> do you use?  Any
> and all input would be very welcome!
> Thank you,
> Kirsten
> ****
> Kirsten Klinghammer
> Rescue, California, USA
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Christel Kasselmann, 
author of the best current authoritative text on aquatic plants 
will be a featured speaker at 
The Northeast Council of Aquarium Societies 30th Annual Convention.
March 18-20, 2005 at the Marriott Hotel, Farmington, CT
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