Heating Nano from the bottom

[midknight]

I was wondering if anybody has tried to heat their tanks externally. I was thinking of putting a false bottom on an old acrylic tank. Fill it with sand and a heater coil and use this instead of putting the heater in the tank.
Right now I have 2 10 gallon one in the bedroom (soon to be replaced with a 25 gallon tall & 20 gallon refugium) and a 10 gallon in the bathroom with an old Emperor 280 as a mini refugium.
I now have my hands on an old acrylic 5 sided 7.5 gallon that I was going to setup on my desk at work. With this I was going to put the false wall inside to make the refugium.
Now I am sure I could build the false bottom easily enough but what ill effect might it have heating this way?

 

[Agu]

Where and how the temp sensor reacts would be an issue imo. Would the temp go to extremes ???

 

[midknight]

I am thinking one of the major problems would be the time delay between reaching a temperature, having the heating element turn off and the time it would take for the sand to cool back down.
But I am worried that if you heat the sub straight would it harm the things we want to grow in it?
Would it help things we don't want to grow?
These and other questionââ"šÂ¬Ã‚¦ Enquiring minds want to know.

 

[chocolateblnt]

Are you thinking of like a reptile heating pad?! I would go with something like a Mini Hydor Heater just less overall headache/doubt of actually working ... also prob. the same price wise.