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Re: Booth's Heating cables & plant growth

> Date: Thu, 06 Jul 2000 13:57:20 -0400
> From: Dwight <boukmn at mindspring_com>

> Great! So I'm NOT crazy!  Now why exactly does this occur?  I don't like
> mysteries!  

Eh, if I knew that I would be rich and famous. 

> The only explanation that makes sense is 12-18mts is the length
> of time it takes an "almost optimum" aquarium to build up serious
> alleopathic compounds that will inhibit plant's growth.  What do you think?

I don't think I would agree. We spent lots of time vacuuming gravel and moving 
plants around so I would discount alleochemicals. 

My preferred hypothesis is that the substrate supplies some/most of the 
nutrients that plants need, especially/maybe trace elements (iron, etc). If 
there is no mechanism to replace the nutrients that plants use, the substrate 
becomes relatively infertile. It will still support some growth so the plants 
don't die. But the Liebig Minimum Law comes into play - the plants can't get 
enough of all the nitrients they need (or perhaps only a single specific 
nutrient that is best supplied by the substrate) and that shortfall becomes the 
limiting growth factor no matter how much light and CO2 and what all you throw 
at it. 

> BTW, what's your opinion on those "hot water" substrate heaters...do they
> work at all ?  How does their performance compare to traditional electric
> wire heating cables?

I've never used them so I feel reluctant to comment. My *feeling* is that they 
can't generate enough heat density to be useful. 

Earle Hamilton (used to be (still is?) on this list) built such a system using 
PVC and he had great success with it. He had a long article in AFM some yers ago 
describing the system and how to build it. I think he ran the water through a 
closed PVC pipe system and used a heater and pump to source water at 95 F. I 
believe he reported great long term results. 

George Booth in Ft. Collins, Colorado (booth at frii_com)