Is this Cherry Barb behavior normal?

[Phinny]

3 weeks ago I introduced 11 juvenile cherry barbs (~1") into a planted 10 gal tank. Up until a few days ago they were actively swimming around and eating whatever I fed them (flakes, nano pellets, Repashy, sinking wafers, zucchini). The past few days I've noticed they are mostly grouped around the center of the tank and hovering, not swimming around much. They also show much less interest in food. I have a gold danio in the tank but she mostly ignores the barbs. She has been feasting lately because the barbs haven't been competing with her for food.  Water parameters have been consistent throughout (0 NH3, 0 Nitrite, 40ppm Nitrate, pH 7.2, temp 76 F). Any ideas what might be going on?

 

[FrozenFins]

Your nitrate is high, try to get it down to 20 ppm

[Phinny]

I got my nitrate level down to 20ppm 3 days ago. As of today, the cherry barbs are a little more active and eating but still somewhat sluggish compared to how they were a week or two ago. Is harm from high nitrates reversible or will they be permanently impaired?

[Colu]

As long as you have plants 20ppm of nitrate  is fine  I would just monitor if eating ok  some barbs and tetra like to hover in one part of the tank  

Edited December 23, 2020 by Colu