I keep reading shimmies is common in mollies & guppies. I have mollies, guppies, tetras, & bottom feeders. The other night, I noticed one tetra looked like it was dancing, but it also didn't look right, & didn't stop...hasn't stopped. I knew my tank had high nitrates, but I had already gotten them down before this started. Found out that, for the 1st time since I've had this tank, my pH has dropped to 6.4 - it's normally 7.6. My tap water has high pH, so I started doing 25% wc, hoping the pH would go up, but slowly. My question, is it possible for tetras to shimmy? And how long can shimmies last? That is the only fish doing this, & I feel it may not recover.