I realised today that the sous vide’d water and my Anova cooker are a perfect recipe for fish tank water changes. After a cook, when the water has cooled enough, it’s surely perfect. The water has circulated for likely 1.5 hours, removing the vast majority of the chlorine and I’m guessing that if the chlorine doesn’t kill anything nasty the temperature probably will. I (believe I) can set the temperature on the Anova to that of my aquarium (perhaps 26C/79F) so I’m told when it’s perfect.
Perfect result for my fish, no effort required, by product resource.
The one “gotcha” is that the water is going to be harder than it was originally - as you’ve had some evaporation, so there will be more minerals in the water (tends to accumulate on the sides of your enclosure). Less so if you have a sealed enclosure that limits evaporation.
I’ve found that the water can sometimes pick up odors and even a slight bit of flavor depending on what I’m cooking. Even trough heavy vacuum seal bags, certain herbs, garlic and rosemary in particular, and chili peppers, tend to permeate through for some reason on longer cooks.