Nice build. Did you order a free sample of the heyco or bought? If latter, I could have saved you some money by sourcing the beyco bere and sbipping it to you with the inclusion of a 2cm piece of clear acrylic for $10 or at least posted you a piece of acrylic only for $2.
Also, I think it is best if you have water enter from bottom and leave from the top so that there is always water in the chamber. I have hardly any issues with heat loss as the heater is on occassionally and we have been getring some very cold nights like 1 degrees here. I also think you should swap the white plumbing tape for the pink premium one.