Talking to your wife about costs is absolutely the best way to go. I know some people have their SO get mad about how much they're spending, and it can often be prevented by just talking about how much is reasonable. Spending money on something for your SO, or encouraging them to spend on their own hobby, can also work- assuming there's free spending money to be had. If there isn't much spending money available, well, maybe it should go not exclusively to corals anyway.
Does your wife like nice chocolates? Ordering some as a "thank you for not killing me about all the fish" present might be good. Or, heck, try and bake something. People usually like homemade cookies. I have a couple good recipes, if you'd like, for things that are easy to bake.
She did just get a house that i didn't really want. I think this a fair trade. But i'll get her chocolates too!