Re: Aquatic Plants Digest V1 #132

Regarding use of air line and bucket with heater for getting a substrate 
heating system, --- The airline would 
be restricted too much which would greatly reduce the flow rate.  A 
complete analysis of this whole subject was written up in AFM, July'95.  
Get a copy and pay particular heed to the side bars.  Your bucket 
approach would work OK but heat loss from the bucket would be 
Again, read the AFM article to know what we are talking about.  Phillip 
Smelt and I built two systems, a closed loop and an open system.  They 
continue to work great.  Your airline suggestion is an open system.  
Replace the bucket with a tiny filter box or something just big enough to 
hold the power head and you will have a workable system
One thing we did not discuss in the article is that it is possible to 
avoid using a thermostat if you know exactly the wattage that will 
properly take care of the tank.  By using a timer (interval timer where 
it can be on for x minutes per hour) it is possible to compute the time 
needed for a given amount of heat.  These timers are expensive and 
probably would be more costly than rigging a thermostat as we describe in 
the article.  It is unfortunate Aquarium Systems or some other company 
does not offer a good thermostat so you wouldn't have to jury rig the 
unit like we did.  
You can inquire if you have specific questions but read the article first.
Regards, Earle Hamilton