I have some fish questions. Yesterday, we got two scout fish, a Zebra Danio and a Guppie. The Zebra Danio seems fine, but the Guppie has been hanging out at the top of the tank a lot and swimming in place. This morning I when I fed them, the fish swam to get a little bit of food and then went back to the top of the tank. I tested the water, and the nitrite was a little bit above zero so I put the nitrite down stuff into the tank. During the day, for a period of time the fish was swimming around. When I got back home today it was at the top of the tank again. I fed it and it ate the food. It swam a little and then went back to the top. Then I tested the water again and the nitrite wasn't completely at zero, so I put some more nitrite down in. My fish is still hanging out in the same place at the top of the tank while the other fish seems fine. What is wrong? I think it may be dropsy. Doesn't appear to be paticularly bloated though.