Heat mat and Temperature enquiries for D. leucomelas

[dbizal]

I am using Degrees Celcius (UK) so I think for D.Leucs I need the Viv to be at around 24-26 Degrees. The Viv sits at around 22 during the day and drops to around 18-19 at night which is too low from my understanding? This is without any heat source other than the LED floodlight I have but that doesn't put any heat into the Viv from what I have been told.

I have planted half of the Viv so far (I am currently constructing a water bath to capture water from the waterfall and create a bath and stream of which will keep the water from being in direct contact with the substrate)
This is how the Viv looks at the moment:


I was thinking about either just getting a heat mat and fixing it to the side of the Viv (which isn't too aesthetically pleassing) or getting a Ceramic Heat emitter of which I could possibly fix up to a dimmer to keep the temp fixed and turn it down at night... It is a shame that the Flukers ones are so expensive and I have to import them to the UK... so for now I think the heat mat might be a better option.

[dbizal]

I was thinking about maybe getting a Ceramic Heat Emitter with a fitting and then plugging it into this? Dimmer Socket Switch Light Table Lamp Mains Plug in. Free first class Delivery | eBay

Do you think this would work?