I have 2 red ryukin in a 50 gallon tank. I've had them about 5 months, since someone moved (they had them 2 1/2 years), and they told me there was little I had to do with them besides feed them. (I now find that's not true!) In fact, when I first got them, all we did was fill the tank with water from a hose, and put them in. When the big one started being upside down, I looked online and found about testing the water, and at that time the ammonia was 6.0 (I bought strips - I now find I should have gotten the test drops). I added anti-ammonia stuff, and started removing and adding water, but only have 4 1-gallon jugs, so I can only change water a little at a time. (I add chlorine remover before adding the water to the tank.) The ammonia is down to 3.0 - I know it should be 0, but it's taken a week to get it down. (With such a big tank it's hard to do a large water change.) Other numbers are: NO3 - 80; NO2 - 0; pH - 6.0; KH - 0; GH - 180 (numbers are approximate since I used strips). The second fish gave me a scare - he was lethargic, just sitting on the bottom last weekend, then seemed better but got a couple red marks on his "chin", but they were gone yesterday, and he's acting normal. So I'm concerned about the bigger one, floating on the top, and not eating.