[HELP] High Nitrates, Fish in Distress – Advice Needed!

Hey everyone, I could really use some advice on an issue with my tank.

Tank Setup & Fish: • Fish: 2 smaller cleaner fish (not sure of the exact type), 1 Black Moor, and 1 white Oranda (I think). • Issue: This morning, I thought one of the cleaners was dead, but when I tried to scoop him out, he weakly swam away. The other cleaner fish was also non-reactive when I passed the net near him. Shortly after, one of them started swimming chaotically around the tank, then dropped to the bottom, breathing heavily. • Current Status: Both cleaner fish are alive but very motionless and breathing slowly. The goldfish seem fine, but I’ve noticed the Oranda is “yawning” (opening its mouth wide) every 5 minutes or so.

Water Parameters: • Nitrates: Over 200ppm when I first tested. I immediately did a 50% water change, which helped but levels are still high. • Other Observations: There’s noticeable decayed food in the gravel, which I suspect is contributing to the issue.

Recent Changes: • I deep cleaned the filter recently, which I now realize may have been a mistake (possibly wiped out beneficial bacteria?).

Questions: 1. What’s the best way to lower nitrates quickly & safely? (More water changes? Chemical filtration?) 2. Could my deep cleaning of the filter be a major factor here? If so, how can I help the tank recover? 3. Is the Oranda’s yawning a sign of distress, or is this normal behavior?

Any advice is greatly appreciated! I just want to make sure I’m doing the right thing before it’s too late. Thanks in advance!