Re: Undergravel heating

> From: Harold Wong <hgw at math_ucla.edu>
> I just installed an under gravel heating coil for my plants. After leaving
> it on for a day, the gravel is over ten degrees (about 84 degrees) above the
> initial temperature. The question I have is, how warm is too
> warm before I start cooking the roots of my plants?
> It's a 50 gallon tank, w/30 guage wire at 12 volts. Thanks.

We have an oversized Dupla coil in our 90 g tank (250w) to support 
discus.  For a water temp of 82 F, the gravel near the coil was 92 F, 
decreasing to 82 F at the top of the gravel.  We noticed no ill
effects in the plants.