I usually only have my lights on for a short time when I want to watch the tank. I also have a window planter that is plumbed to sit on top of my canopy filled with Pothos plants that help with nitrate reduction to reduce the frequency of larger water changes. I also use any water I get from water changes to give the lawn a little boost.
The fish, I suppose, you could also say are "green." I only buy fish that I can obtain locally.
Unfortunately, I still see a lot of green when I pay my electric bill. :x
When buying anything electric I carefully scrutinize the amperage draw as a major consideration in purchasing said item. I am not tempted to "over" filter my tank by keeping stocking at moderate levels. H2O from WCs is used for house plants or exterior landscape. Minimize amount of time tank lights are on.
LED lighting...but thats about it. We recycle a lot, and I would agree I spend about as much time looking at my tank as I do online like the above said so there's that....
Also some rare/semi-endangered fish in my 100 gal...
I'd say every fish tank is inadvertently green in many ways...simply for the fact that it promotes enjoying wildlife and if you follow some guidelines...promotes ethical, nature-friendly, US-bred ( or not wild caught) and sustainable fish raising...nothing wrong with wild caught..but for some fish wild-catching just adds to the strain on an already strained wild population.
Just my plants and algae. I try to keep things as natural as possible, but I don't worry about the cost of filtering or lighting or whatever it takes to keep a tank healthy. It is not a cheap hobby by any means.
I never calculated it out but really how much does a filter/heater cost to run for the year it cant be thaaaat much compared to everything else we use. And no this is NOT a cheap hobby pretty sure I spend more on fish and related expenses than on any other hobby I have ever had