Large oscar fish

Question
QUESTION: Hello Mr. Coleman,
 First off I have a 55 gallon fresh water tank that has a undergravel filter with two power heads and a hang on the back filter. My water conditions are all fine and I check the regular. The tank houses two large Oscars one red one that is about 10 inches long and the other is a tiger Oscar that is 9 about inches long (nose to tail). My concern is that for the past almost month my tiger Oscar is going through periods of time where it will just lay on the floor of the tank and show no interest at all in things. It will sit that way for at least 30 minutes at a time. It still eats fine and they are not overly aggressive, they have a varied diet peas on occasion, cichlid gold pellet food, some worms and crickets. I switch it up from day to day so they don't get bored or under nourished. They outward appearance is just fine and all appears fine, but the periods of inactivity do concern me and was wondering if you have any idea what could be causing it. They do fight a little but that is never any different than when I purchased them about a year ago when they were less than a inch big. Are they just starting to come into maturity or could there be something wrong. Thank you for your time and expertise, I love these two fish dearly and would hate to lose them.
Thank You,
Heidi

ANSWER: Hi Heidi,
 I am always concerned when people say that their "water conditions are fine".  Are you trusting a test kit to tell you that?  Those little test kits are notoriously inaccurate.  For a 55 gallon tank with two adult oscars, I STRONGLY recommend that you be changing 25% of the water once a week, every week, regardless of what your test kits say.  Declining water conditions are most likely the cause of the behavior you are seeing.

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>


---------- FOLLOW-UP ----------

QUESTION: Hello Mr.COleman,
 I do use the little test kids but did recently take to the pet shop and they did test it for me. I do do 25% to 30% weekly water changes,that happen every Sunday, faithfully for the almost entire year that I have had the tank and the fish. I realize that the changes are necessary if i want to keep my fish happy and healthy. The pet shop owner where I purchased the fish as babies said that they may be just becoming mature and ready to make. And because there is nobody that they want to mate with or because they may be same sex this could be causing them to be depressed I guess that you could say. Could this be the case? I have always been careful to try to keep my water and living conditions for my fish healthy.

Answer
Hi Heidi,
  It could be that they are maturing but that generally doesn't result in less activity, quite the opposite.  If they were the same sex, they would likely fight until one of them got rid of the other.   

  By the way, oscars will normally lie on the bottom of the tank. That is part of how they hunt. They lie on the bottom and wait for little fish to come by, then they "jump" up and eat them.

  That said, oscars do get depressed and this can last for days or weeks. The most common cause of this is changes in the people situation in their "home".  I know of many cases where something changed in a household (e.g., a kid goes off to college) and the oscars get very depressed for weeks on end.  Oscars are very intelligent and perceptive and they respond to each person differently, so they are easily capable of "missing" someone.  

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://ciclidresearch.com>