Not as long as it’s stable. I kept harlequins in gh
of one for years and they bred for me! A couple even survived in the community tank somehow!
Are you testing after a water change? If there are chloramines in your water and can cause a slight ammonia reading that will go away quickly and isn’t anything to worry about.
Both at night? Could oxygenation be a problem at night (sometimes happens if you have live plants) if you look into the tank right before lights on are the fish at the surface?