I'm currently having a problem with my black moor. He's been very lethargic for the past day but I thought it would just pass and then today I see that he's really bad. Struggling to get up and breathe. He keeps getting worse. I did a full tank clean and put him back and it looked like he was doing better for about a minute and now he's struggling to breathe again. I have a ten gallon tank and I've never had any problems with him before. Please help, I don't know what to do, I'm so afraid that he will die.