Sick Oscar :(

[fishRfriends]

One of our oscars isn't doing so well, and tonight he is in the worst condition I've seen him. We thought he had hole-in-the-head a few months ago and treated him for that but no improvement, but he didn't get any worse and seemed to be stable, so we thought maybe he was just scarred (he did have a gash on his side when we first bought him, so we know he had been in at least one fight). Recently however he has taken a sharp turn for the worse. It started at first by him laying on his side alot. He would lay at the bottom of the tank or stay close to the surface while laying semi-sideways. Just today I saw a white-stringy substance coming out of his gills. The holes all over his body are still there, and now I don't know if they could be indicators of something much worse. He also seems to be missing scales in some places. He shares a 75 gallon tank with another oscar, a common plec (who is very small and will be rehomed as soon as he is a bit larger, a chinese algae eater, and a fairly small pictus catfish, all of which show no symptoms (we are trying to rehome the catfish and the algae eater as well, as I'm sure this is overstocked). His appetite is fine and he has no problem battling the other for his share. I will try to get pictures later if they will help and will get tank stats as soon as possible. Thank you for any help!

 

[Colin_T]

Sounds like it is getting bashed by the other oscar. Poor water quality will also cause problems to cichlids, especially in regards to causing hole in the head disease. Try doing daily 50% water changes and gravel cleans for a week and see if it improves. If not then separate the two oscars and see what happens.

 

[fishRfriends]

Thanks for the reply. This is my parents tank and I just told them that and they are doing a water change as we speak .
I just checked the stats for them...and they are terrible. We have had this test kit for ages and I don't know if they expire, but these results just don't make sense. This tank has been set up for about 5 years.

pH: 6.2
Ammonia: 3.0ppm
Nitrite: 0.0ppm
Nitrate: 160ppm...

Of course these scared us, so we did a test on tap water, and the ammonia came back 0.0ppm, so it seems logical. I just don't know why the nitrite would be 0 and everything else so high. I did find out that my dad rinses the filter media in tap water when he cleans the filter, would that do it? Or is the tank really way too overstocked?

Also, whatever appeared to be hanging off of his gills yesterday is completely gone, so I don't know what that could have been.
Thanks for any help.

ETA: Here are some pics:

And the potential bullying culprit:

 

[Colin_T]

The fish is suffering from a really bad case of "hole in the head disease". This is shown by the scars all over the face and head. It is brought about by poor water quality encouraging a pathogen called Hexamita. You need to clean the tank up by doing more water changes and gravel cleans.

The ammonia level will be from the filters being washed out under tap water. You want to wash the filter materials out in a bucket of tank water. When they are clean put them back in the tank and rinse the filter casing out under tap water. Then put the filter back together and fill it up with tank water before turning it back on.

Big fish like oscars need a water change at least each week. If they don't get enough water changes then the nitrates will go up, and they have. If you do a daily 50% water change and gravel clean for a week that should drop the nitrates pretty quickly and help the oscar recover a bit from the disease. You might need to treat the disease afterwards with something like “Waterlife Octozin” or Metronidazole, available from the vet.
If the fish are big (move than 8inches long) then they only need to be fed once every couple of days. The more food going in the tank, the faster the nitrates will go up and the more water changes you will need to do to keep them low. You want to keep the nitrates as low as possible and preferably below 50ppm.

The stuff hanging off the gills was probably excess mucous. Fish have a mucous coating on their body and if they are stressed they produce more of it. This can make the fish look like it is covered in a milky white slime or just have filaments and slime hanging off it. Poor water quality is the biggest cause of stress in fish and the subsequent formation of excess mucous.

 

[fishRfriends]

Thank you so much! I knew the stuff about washing the filter media in tank water, but I guess it was just second nature to me and I forgot to tell my parents about it, and just found out they were doing this. So that will be fixed right away! The tank gets cleaned out once every 2 weeks, so that can definetly be upped!! And we had the opposite logic--big fish means they must eat more often. So would every other day be good to feed them?

One more question, is a 75 gallon ok for the oscars if the water changes are maintained every week, or does one have to be rehomed? Some places say a 75 isn't even enough for one, while other says its fine for 2. I'd hate to separate them as they seem to get along so well, but if it has to be done to keep them healthy then we will see what we can do. Also, does the pictus catfish have to go? He stays at the bottom and I remember reading somewhere that since the oscars and the cat occupy such different areas of the tank, stocking rules are a little different.

Thanks again for your help!

 

[Colin_T]

Big predatory fishes like oscars are fine being fed every couple of days. It is more natural for them. Out in the wild they are ambush predators and don't always get food each day. Often they will catch and eat a fish and then not catch another one for 3 or 4 days. Every second day is a good way to go for feeding them. It reduces the amount of food going into the tank, thus reducing the load on the tank and keeping the water cleaner. It also helps prevent the fish from becoming over weight and suffering the associated health risks

A 75g tank is borderline for an adult pr of oscars. As long as you keep the water clean they will be fine. Weekly water changes will help keep it that way but you might need to do it twice weekly. You want to measure the nitrate levels in the tank and see how they go. If the nitrates go up rapidly during the course of a week then you need to do more water changes, or reduce the load on the tank, (ie: cut back on feeding or remove some fish).
If the nitrates don't go up during the week (or only go up a little bit) then the current water change regime is fine.

For the long term health of the fish it would be preferable to move them into a bigger tank, (say 150gallon). This would mean less water changes to keep the water clean and a more stabile environment for the fish. However, as long as the water is kept clean they should be fine in their current tank.

The pictus should be fine in the tank and will be ok on the same feeding regime as the oscars.