Hi Guys I have just started my outside AP system. I have 3 grow beds above a 1000L IBC fish tank. Where I live it gets down to about -5 Degrees C in winter.  I have about 200 Blue Tilapia in the tank. All is fine at the moment, I have two 300x heaters in the water and it maintains at 27 degrees C. But winter is not far off, can I have some ideas on how best to keep the water about 20C during win…