RSS Facebook Twitter YouTube




Oscar is not eating, breathing heavy, listless…Please Help!

Home Forums Fresh and Brackish Water Fishes Oscar is not eating, breathing heavy, listless…Please Help!

Viewing 7 posts - 1 through 7 (of 7 total)
  • Author
  • #302689


    Hello everyone,

    I thought my Oscar was just being temperamental (as usual), however, she/he(?) has stopped eating, is breathing (fairly) heavily and generally looks inattentive. I’m very worried since he is usually ravenous for food, breathes normally through the gills and is very attentive (especially for food)! also, I just saw him resting on the gravel, on the ventral/’stomach’ side. 


    Here are some of the particulars about my tank:

    75Gal Tank, 2 Aquaclear 110 filters (one filter that runs 24/7/365, and the other filter that runs approx 8 to 10 hrs/day).


    Contents of tank:

    2 Oscars – one approx 11inches (the one with the problem) and one approx 9inches

    1 Jack Dempsey approx 5 1/2inches

    1 Geophagus approx 6inches

    1 Convict approx 4inches


    Water change of 25% once a week (including gravel cleaning and inside glass cleaing)

    Clean both filter approx once every 2months

    sponge, carbon filter media replaced approx once every 4 months


    Please help me!!!  noexpression.gif


    Thanks, Rob



    Hi Rob,

    Sorry about your fish. I’m not an Oscar keeper but a few things that jump out at me.

    Are you testing your water parameters? The usual Ph/ammonia/nitrite/nitrate.

    It seems like with that fish load 25% weekly may not be enough.

    As for your filters why do you turn the one off? By doing this you’ll be killing off the bacteria that process the massive waste those large fish produce. Aquaclear sponges last forever so no need to replace those and I’d definitely replace the carbon with biomedia, as much as you can fit in the filter box.

    That sounds like a big old Oscar and maybe it’s just his time? Best of luck!


    Edit: Depending on what all you have in that filter, and how long the carbon has been in, the carbon may have gone biological and may be housing most of your bacteria. So if you do replace it, it would probably be better to do it in increments rather than all at once.



    Appending to what Plaamoo said I wonder about
    “Clean both filter approx once every 2months”
    Actually when there are two filters, they should be cleaned one at a time. With large bioload, cleaning both may kill the biocycle. And if you want to use carbon (not saying you should!), you should replace it more often, like every month, because it loses its activity quickly.



    Hi Rob,

    unfortunately I can’t tell you either what’s wrong with your Oscar and since that is your actual question, I hope you don’t mind too much if I elaborate on the point, both Jim and Mike have made.

    The only filters, which should or rather can be run “part time” are chemical filters and mechanical filters such as uv filters for instance. As Jim has pointed out already, whatever amount of bacteria can settle in the filter media during the 8 – 10 hours operating time will be dead long before the “resting time” is over. Thus, you initiate a micro cycle every time you switch that filter on again alas with no benefit whatsoever to your tank and fishes. In addition, when you switch off, you reduce water agitation = gas exchange = oxygenation.

    Carbon as a filter medium ONLY makes sense if you have to eliminate chemicals and/or heavy metals in your tank water. But if you had a problem with that, be assured that the tiny carbon pads, which fit your filter, would be entirely insufficient. If you feel that your tap water needs that kind of filtering, you should do that before you do your water changes.

    From my experience, a biological filter should ONLY be cleaned once its performance decreases noticeably. I know this sounds contradictory to what is commonly taught, but the “scheduled cleaning intervals” are actually aimed towards the pre filter parts and (useless) carbon pads in the filters. If you eliminate them entirely, your filter will “tell” you when it needs cleaning.

    It is a good thing to have 2 filters running but only if 1. they both run 24/7 and 2. if you, as Mike has pointed out, clean them alternately. This way there’s always one filter doing the job, whilest the other can recover from the violation of it’s biological balance.

    Now, if your Oscar is suffering from any ailment other than age, it most likely is caused by the tank water and your “unusual” filtration schedule could be the cause.






    Hi Rob!

    I am feeling so sad for your fish.

    You mentioned that your Oscar is breathing heavily. Heavy breathing could be a case of lack of oxygen in the water, have you made any adjustments to the pipe that returns water back into the tank? For a good supply of oxygen plenty of surface agitation is required.

    Also you need to check and clean your filters.

    Please let us know how is your Oscar now.



    Dear Alan Young. I fear this is not the site for you and will be forced to take action should you continue to post nonsense on these boards. I also notice a link to a commercial site in your signature which is against our rules – this will now be removed.



    Hi Rob, is your fish doing any better now? I had a fish, gasping- went off food and it was increased nitrates. I hope your Oscar is doing better.

Viewing 7 posts - 1 through 7 (of 7 total)

You must be logged in to reply to this topic.