The tank at the end of the roof flow looks like a good idea. And I also remembered that controlling the amount of water being pumped to the roof may also control the temperature. With lower speeds at night (is a full stop possible?), not only the tank remains more termically isolated but also will prevent large amounts of CO2
coming from the algae on the roof to enter the tank.
I'm planning on having the tank running without fish for an year to make adjustments.
I was reading the article on glass thickness. Lot's of talking about the way different glasses crack. I recently posted a thread about "large scale catastrophe". I regret that title... you can imagine the images that came to my mind while reading that article. But the calculations are extremely usefull at this stage so I can have an idea of the costs.
I'm planning on having just two larger windows and not that large really, considering the tank is 30m x 20m x 2.5m. Around 7 meters long by 2 meters high. All the others will be much smaller.
The wall thickness for a 2.5m tank is within what's normal for exterior house walls around here. Traditionally houses have thick walls (sometimes nearing 1 meter).