sorry to hear that, that is why i never like to leave home to my grandmother's XP i worry too much, and tell EVERYTHING on how to care for them, when to feed them, how much for a specific fish, when lights go on, and if so how to clean it
I'd still not be talking to my mother in law if she did that to my fish. I love my fish. My inlaws think I'm a nut job because I name all my fish and treat them when they get sick, I talk to them and show them love and adoration. I know my fish like they were people. I can even tell what sorta people they'd be if they were human. I improve my tank for the fishes sake not for asthetics. You'd do it for your cat so why not your fish. I had a slight falling out with my mother in law for her "If it dies it dies" stance and the "I'll just flush him" instead of finding her molly a new home when he started to terrorise a balloon molly. I will never EVER allow my mother in law to look after any of my pets because of this. My hubby doesn't see my reasoning either but he would defend her to the death regardless. She is his mum after all. But I do think you need to say something to her. Explain to her why you're so upset, after all you do deserve and explanation for blatant stupidity. Who puts gravel in a fry tank with live fry in for gods sake? Why would you remove all the decor from a tank but not clean the fish out? Sometimes accidents happen. Fish sometimes die without explanation or one might get sick and an unexperienced fish keeper might not know anything about disease but this just looks like neglect to me.