ghost knife and clown loaches

Question
hi i did a water change 2 weeks ago and had a large ghost knife that didnt want to eat after this. He keept going to the top of the tank and i checked all the params they were very good. Its a 150ltr tank and has been running approx 3yrs. The ghost died but now the clowns are swimming around fast and i know something must be wrong  but dont know what. Thanks

Answer
Hanging at the top is usually a sign of lack of oxygen. I would add an air stone if you had one to put more oxygen into the water while you are trying to figure out what has happened. If you have one already, I would either turn it up or add another one.

You did not say how many or what type of fish you have in the tank (outside of the ghost and clowns). Can you please e-mail me back the type of fish, about how big they are and what type of filtration you are using? Also, if you have a master water test kit and can provide me with water parameters, that would help greatly. I need this info in order to help give me insight into what can be happening.

Thank you and I will await your reply.   ;o)