Confused about Oscar death?

[Zak03]

So, I've had this red oscar for a few months. Since around the beginning of December. This dude was a beast of a fish. He was a juvenile. He has lived through an ich infestation, lived in a tank while it was being cycled, and has outlived two other juvenile tiger Oscars. He's never shown any signs of weakness.
looked very well fed. I did not overfeed; I fed him pellets a few times throughout the day, small amounts each time. i wasn't worried about excess food on the bottom of the tank cause i knew the catfish will eat it at night. i still sprinkled several pellets every evening for the sun catfish (3") (every once in a while, I would cut up a small frozen shrimp and put in the tank for the fish to eat. all the shrimp bits would be gone in a couple of days). the oscar was happy, healthy, and growing. i did a 40 % water change (40 gal tank) on Saturday, April 13th. my water parameters were good.
then soon after the water change, i took in a dinosaur bichir (2-3") and a 2 African dwarf frogs for my brother. the oscar became interested in his new neighbors, it was actually rather funny because he seemed quite confused with the bichir (we kept him with the bichir for a few weeks when we first bought them, so we were wondering if he remembered the bichir or maybe was having de ja vu). there was no bullying. the fish and frogs all seemed happy to be neighbors.

but then on Thursday, April 18th, I woke up and my oscar was just lying dead on the tank floor. he just up and died randomly and I can't figure out why. food was good. tank mates were good (don't think it was overstocked cause fish are still small), water conditions were good.

Does anybody have any ideas why my oscar just randomly died, but my other animals are doing just great? the bichir, frogs, and catfish were all putting on some size. they were well fed (i was feeling proud too, cause I was gonna return my bro his animals and they were gonna look bigger and better than ever)
so, does anyone have any clue why my oscar decided to die on me?

 

[duanes]

There really isn't enough info here to tell what's up.
What was the nitrate level, prior to water changes? How many water changes and what volume per week?
What about pH before, and after water changes?
If it were me, on a tank that small, I'd be doing 50% water changes at "least twice per week.
From the info given, I have a feeling the tank was on the edge with just the old inhabitants, and then adding the frog and bichir put it over the edge turning the water to thick urine soup, and either crashing pH, or just plain making it a toxic enough soup to be unhealthy.
To me, a 40 gallon tank is not big enough for even 1 oscar, much less all those others.

 

[Matteus]

Also not sure if you know this but those African dwarf frogs are the natural diet of wild bichirs. So at some point that may happen.

 

[DawnMichele]

Sorry for your loss.

 

[Zak03]

There really isn't enough info here to tell what's up.
What was the nitrate level, prior to water changes? How many water changes and what volume per week?
What about pH before, and after water changes?
If it were me, on a tank that small, I'd be doing 50% water changes at "least twice per week.
From the info given, I have a feeling the tank was on the edge with just the old inhabitants, and then adding the frog and bichir put it over the edge turning the water to thick urine soup, and either crashing pH, or just plain making it a toxic enough soup to be unhealthy.
To me, a 40 gallon tank is not big enough for even 1 oscar, much less all those others.

i recognize and respect that your experience and knowledge in the fish keeping hobby is very extensive and far better than mine, but I want to disagree with you. all the animals are smaller than 3 inches. At one point (before the new tankmates, so 1 red oscar and two catfish) have gone for two weeks with no water changes. I checked my water parameters and the Ammonia was 0, the Nitrites were just starting to go up, and the nitrates were below 40ppm (i don't remember the exact values). And so, the water change on April 13th was just over a week since the previous water change, so Iwas being kinda redundant/overkill with the water change. but I still decided to do it since i had some spare time and didn't know if the next weekend I would have enough time.

i did a 40% (at least) water change on 40 gal, so that is a minimum of 16 gallons. and considering it was only five days for a tank that can go two weeks without a water change (although new tankmates, so i would play it safe and say it could go only about a week). my brother and i have never had issues with the acidity level cause we have well water. and his tank has been up and running for quite a while. Ph is not an issue.

 

[Zak03]

Also not sure if you know this but those African dwarf frogs are the natural diet of wild bichirs. So at some point that may happen.

well, we didn't know they were the natural diet of bichirs, but yea, we knew he'd eat them once he grows big enough. We're just keeping them together for the time being. Thanks for the info though, wasn't aware.

 

[Zak03]

Sorry for your loss.

Thank you. I was running late that morning so I didn't have time to process it. completely forgot about until I got home much later in the evening.

 

[AnthonyFish20]

Was ur oscar eating a few days before?

 

[skjl47]

lived in a tank while it was being cycled

shrimp bits would be gone in a couple of days).

40 % water change

If it were me, on a tank that small, I'd be doing 50% water changes at "least twice per week.

tank was on the edge with just the old inhabitants, and then adding the frog and bichir put it over the edge

a 40 gallon tank is not big enough for even 1 oscar, much less all those others.

i recognize and respect that your experience and knowledge in the fish keeping hobby is very extensive and far better than mine, but I want to disagree with you

Hello; I am with Duanes comments all the way. Duanes may not have the exact answer as he is not on the scene as are none of the rest of us but I tend to consider his comments worth considering.

1 red oscar and two catfish) have gone for two weeks with no water changes.

nitrates were below 40ppm

considering it was only five days for a tank that can go two weeks without a water change (although new tankmates, so i would play it safe and say it could go only about a week).

Hello; These are interesting rationalizations but not backed up. A tightrope tank (One on the edge) can go bad in days or even hours. That fish survived two weeks between a WC does not make it follow one week is safe. One way to get clue is the waterparameters with a test kit. 40ppm nitrates is considered high end by many. Shrimp laying around two days is decomposing during that time.
We did not get into the filter and if the media has ever been changed or cleaned.

Good luck

 

[Zak03]

Was ur oscar eating a few days before?

yea, he was eating the night before. he was still interested in the food