Who Gives A Fish Forums

20 ppm isn't terrible, but you're right to wanna lower it. What's your tank size and stocking? Overfeeding or too many tankmates can spike nitrates. Also, check your tap water, sometimes it's got nitrates already.

Yeah, my Betta did the same thing when I added a new piece of driftwood. Turns out it was leaching tannins too fast and freaked him out. Maybe something similar's happening here? Check if anything new's in the tank, even if it seems harmless.

Nah, HOBs are solid if you're not overstocking. I've got one on my 40 breeder with a bunch of Guppies and it's chill. Just gotta keep up with water changes and you're golden. What's your stocking like?