Reasons for new fish not eating? Cure?

[duckckpro]

i recently have a newly bought armatus, but still not eating for 3 days i guess, not even interested in anything......
However, a newly bought snakehead and id shark already starting eating a bit, but not aggressive eating type.

The armatus has its the further part of its tail fin melted, i think this is due to low pH? but i think the pH just keep decreasing no matter how I push it up.... so i think this is out of control but only water changes?.....

I think one main thing that stresses the armatus is that there are a 7' knifefish and a 7' catfish in there that scares it... however the new snakehead is just 3' LOL... it ate one feeder fish right when i release it into the tank.... I have tested my water quality, which ammonia is at quite high, would that also stresses the fish??

So... i wanna ask if anyone can suggest any solutions, i think the ultimate solution is seperate it into another tank...... also is that garlic extract really help increasing fish's appetite? i wanna anything a try ;(

 

[fisher12889]

Did you cycle your tank? It sounds like you need to read up on the nitrogen cycle. Ammonia is REALLY bad for your fish, you need to do water changes immediately.

 

[duckckpro]

i know about nitrogen cycle.... but because recently my canister filter is broken i think majority of bacteria may have died... but i fix the filter now... and the level of ammonia is dropping gradually, but at the moment its still high i would say...