So I started a new tank about 6 weeks ago and recently put in a GBTA. It was doing ok but now everyday after I adjust the water salinity and add water it seems aggravated and starts to shrivel and open it's mouth wide open. Every morning I see it and become relieved because it looks so healthy, and then later not so much. I was told an ato could help it from getting this way since salinity won't change so drastically. Any thoughts?
Before (not the best pic usually it's mouth is shut tight)

After

Before (not the best pic usually it's mouth is shut tight)

After
