So there is this kid that I homeschool with who is not very great with animals and by that I mean he kinda neglects then and is mean to them. So I’m 13 and so is he and we are both homeschooled so me and my mom go over to their house once a week and do schoolwork and I noticed he has a fish. He has a 2 year old OSCAR () in a 20 high tank. Unbelievable. And on top of that the filter looks like it has fungus growing on it and the tank hasn’t been cleaned in over 4 months. I managed to convince him to allow me to at least get a new filter, heater, plants and decor, and clean it when I come over. So I know very little about oscars but the only thing in the tank is about 3 inches gravel, four 4” plastic plants and a gator skull decor piece which isn’t that big. So what I was thinking of doing since I’m limted to getting things since I don’t have much money and all my tanks are 10 gallons so I don’t have much extras for him. I was thinking of taking out my xxL amazon sword and putting in the oscars tank, putting my adjustable 50 watt heater in there even though it’s not much but I think the room temp was 77 so I’m not to worried about temp, I was going to put 2 10 gallon filters in there since that’s the largest filter I have and then just some extra hides and silk plants I have. Do you think this will help at least? Also should I do a 100% water change this first time or do a 50% water change every week for 3 weeks that way I don’t shock the fish? Also what should he be eating?