But why is a shame to give it to someone with a much more suitable set up? That's the part I don't get. I'm not going to sacrifice the welfare of my current fish, to keep a fish I never planned to get. The fish is no longer in a tank that's too small for it (and for your own stocking, a 30g is far too small for three 3-spot gourami, so that wasn't planned out well), and keeping it - apart from the risk to the baby cories and seven elderly tetra and livebearers I have, would mean abandoning the dream tank plans I already had until the gourami dies, which could mean years... it makes no sense to keep it, and the set up it might be going to is much better for one of these fish.
Isn't it enough that it's already much better conditions, with clean fresh water, not being poisoned by sky high nitrates and bullied by the rainbow shark (as soon as I put them in QT, the rainbow began following and harassing the gourami, so I had to separate them. So there's a good chance that was also happening before I took them in) getting a better diet etc, and then will be going to a much better set up than it has lived in for the past two years?