When people have issues with their fish right after cleaning out their filters it is often because they overcleaned or used tap water and killed off some of their beneficial bacteria triggering ammonia / nitrite problems (called a mini cycle). When was the last time you tested water and what were the numbers. (Really it will save us time if you look at that thread and answer those questions.)
Honestly your description of what’s normal for him is a little concerning too. Fish knocking themself out on the glass doesn’t really seem normal to me. I wonder if some of that odd behavior could be attributed to the sky high nitrates.
Old tank syndrome. It has to do with when water conditions deteriorate slowly over time (160ppm nitrate) slowly enough that the fish gets used to it. Then the aquarist notices does a large cleaning and the conditions improve (160-> 60) but so quickly it can actually cause nitrate shock (laying on the bottom / listlessness are among the symptoms of this kind of shock). It’s often a dangerous one two punch with a mini cycle that follows from over cleaning.
Why kanaplex, what are you treating? Do you see any signs of bacterial or fungal infection? Kanaplex (according to Seachem) won’t kill off your beneficial bacteria, but will inhibit the growth of said bacteria so if there is any minicycling happening it will exacerbate that problem.
If you haven’t already check your ammonia / nitrite ASAP and rather than using a filter media to suck out all the nitrates rapidly I would recommend daily no more than 30% water changes until things are back to safe levels. Remember that nitrate is one thing that we can test for but it’s not the only thing accumulating. So when you use nitrazrorb you might be getting a false indication of the water quality improvement.
Libertybelle I apologize, I'm new to forums. I'm just trying to figure out how to reply properly. Let me try to clarify: 1. I'm not sure what thread you are asking me to look at and answer questions to? Do you have a link to it? 2. My gourami's thrashing about the tank is of course NOT normal! He started doing that periodically last week. It was ALARMING and seemingly only occurred at night. This behavior started BEFORE the water change, not after. 3. I IMMEDIATELY tested the water, PH normal, no ammonia, no Nitrites. I skipped the NITRATES test at this time. I never got a high nitrate reading before if all other tests were in normal range. 4. Since the water tested fine, and it wasn't due for a change, I left it alone while I searched for answers on why he was doing this random crazy zooming swim. I captured it on video and ran around trying to get someone to help me figure it out. The consensus was he perhaps had "whirling disease" or a neurologic disorder. Both of which they said nothing could be done. 5. 2 days ago I found this NEW behavior of either sitting on the bottom upright or laying flat down. He tries to swim, but drops back down to another spot in the gravel. 6. I retested the water, this time I included the NITRATES and found it to be 160. Everything else tested in the normal range. I IMMEDIATELY changed about 35% of the water. I also rinsed out the filtration system to remove any sludge that may be causing the high level. Retested 24 hours later, same result, Nitrates didn't budge. 7. On day 3, retested and no change. I then added the NITRO ZORB filter pack and added 3 LIVE plants. 8. Today I drove to the small tropical fish store where I bought him 3 years ago. It was an hour away but I trusted the owner. I showed him the video, pictures and he tested my water. Interesting thing is that he found nitrates in the yellow range? So it appears the drop happened quickly as you suggested, but not the cause clearly since he was struggling before the drop. 9. The owner suggested I treat him with KanaPlex, he said he could have an internal infection of some kind, or swim bladder, and that this treatment might work.
I hope it does!! Again, all other fish are acting fine. If it were an environmental issue I would think it would be affecting others. 4 Tetras, 3 guppies, 1 Roseline shark and 1 Plychotomus.
I hope I answered everything for you. If you have the link where I can add more information, please let me know. Thanks so much for your help!