Problem would be at night, especially winter time. Have to switch that unit off to prevent it from cooling our tanks to much. How to prevent the bacteria inside those tubes from using up all the oxygen, changing the water chemistry. When the unit kick back in again, then all that water with no oxygen would be pumped directly back into the tank. What will that do?
If you do connect this up to an titanium heat exchanger coil, that is inside the sump, that would work. As then the fluid inside the coil and sun panel would never be in actual contact with the tank water. No critters can enter and no bacteria plus oxygen issues. Can then use proper cooling fluid that would be better than water for heat exchange. Just need to ensure that the coil would never leak into the sump any cooling fluid.