Fish Floats At The Top Of Tank

[guppyrookie]

my guppies are floating at the top of the tank near the water's surface. Pretty sure they aren't overfed as I feed them very little. I have a 30 gallon tank with an aqueon 40 filter and two sponge filters. i only have java fern and anubias in there. I'm thinking of adding more plants later. help?

 

[nikkifro8994]

Did you check the water? What are the ammonia, nitrite, and nitrate levels? How long has the tank been running? Are the fish just relaxing or do they seem to be gasping for air?