Hello, New to the site. I used to have a large aquarium (60 gal) a long time ago, and recently came into possession of a small 5 gal tank that I decided to set up for fun. I did not realize the tank would be too small for most tropical fish. I have filtered water to my home. I just did my first cleaning of the gravel and a partial water change due to high nitrate levels. My 5 tetras had gone to just 4 and were in distress and no longer eating. Of course there was a waste sludge on the bottom. Once cleaned and water changed, at first all seemed better. Fish were eating again, acting normal. Then water got cloudy. I added some clarifier and it mAde it worse. Fish are gulping for air at surface and acting distressed again. I am adjusting the pH (it was too alkaline) and did another partial water exchange. Water is still cloudy.... What now???