Bad heaters!
How are you doing with the native fish? No nice deluxe treatment of those? Or have you rehoused them during the rebuild? I can imagine that they would be harder to house temporarily because of the cooling needs(though the chillers would heat the room a bit preventing the need for evil heaters) and many of the specimens are a bit larger and more predatory than your tropical fish. Though it seems your budget for the tropical tanks exceed the cold-water during the last years... ;-) You need to tell mister Jens that he needs to step up his game aswell!
We will have at least 4 small tanks up soon for cold water species in the temporary Aquarium. It'll be mostly invertebrates and maybe some pipefishes I think. Cods and most other Swedish fish gets too big
So when we start up the chillers, I'm sure we won't have a problem heating the tropical tanks no more We are more worried about the temperature in the room during the summers. We got one AC now, we might need more.
The reason the tropical part of our collection has grown more than the cold water is the cooling capacity. Our old large cooler broke down and we didn't want to replace it a year before the rebuilding. So some cold water tanks became tropical. It's much easier to keep water at 25 degrees than 12!
In the new Aquarium it'll be a lot of cold water tanks. Both cold as in Swedish waters, but also a system for Atlantic/Mediterranean animals with a temperature around 18 degrees. And a kelp system with temperature following seasons.
And some plans for a 4-6 degrees tank, for deepwater corals like Lophelia pertusa.
So Jens is will have plenty of cold water tanks in two years! (He's responsible for our cold water systems)