Hi, I have a new 10 gallon freshwater tank (4 weeks) with 2 red minor tetras that I added 3 days after I set up the tank. I had the water checked 2 days ago. Ammonia .25 / Nitrite 2.0 / Chlorine 0 / Salinity 0 / pH 6.4 / Carbonate Hardness 1 / General Hardiness 5. My tank has not finished cycling and I am to add, twice this week, a pH stabilizer (I also use Stablity daily). One tetra is larger than the other and nips at his fins alot (all of them). I was told this would subside when other fish are added, but today my little tetra has a buoyancy problem. He seems to pop straight to the top and has to struggle to swim to the middle or bottom of the tank. He ate with no problem today and seems to be as bright as the other one. What could be wrong?