Columbian shark dying

[Newguy125]

I just recently got a new tank I went from a 65 gallon to 125 gallon and it's been about a week week and a half and my Columbian shark is acting Pretty erratic. swimming towards the top of the tank.he has stopped eating and he's just facing towards the front of the aquarium belly facing out. I've had this fish for about 4 1/2 five years no issues this the first time he's ever or she I don't know has exhibited this kind of behavior any ideas would be appreciated. I had the water tested two days ago no issues. I have raised this thing since it was about an inch and a half it's almost a foot and a half in length to know. Additionally I have put some aquarium salt in the tank as well. Is tank mates or an Oscar two silver dollars a pleco a convict and a yoyo loach

 

[JuiceBox52]

@Colin_T might be able to help

 

[ChefAlex]

I just recently got a new tank I went from a 65 gallon to 125 gallon and it's been about a week week and a half and my Columbian shark is acting Pretty erratic. swimming towards the top of the tank.he has stopped eating and he's just facing towards the front of the aquarium belly facing out. I've had this fish for about 4 1/2 five years no issues this the first time he's ever or she I don't know has exhibited this kind of behavior any ideas would be appreciated. I had the water tested two days ago no issues. I have raised this thing since it was about an inch and a half it's almost a foot and a half in length to know. Additionally I have put some aquarium salt in the tank as well. Is tank mates or an Oscar two silver dollars a pleco a convict and a yoyo loach

A little more info would be helpful, exactly describing the tank set up before the switch and to now. Listing your water parameters exactly would be helpful. Not everyone is aware of the basics, like cycling an aquarium, so describing everything from the bottom up would be helpful.

Unfortunately, I see a lot wrong going on already. If the specimen is as you say is almost 18” long, that 65g was incredibly too small and your current 125g is also way too small. Columbian sharks are a shoaling species and really need to be in groups. They also prefer full marine conditions as adults, they only should be in freshwater as juveniles. Since it’s current tank mates are not brackish water species and haven’t perished, I can already tell your salinity levels are not anywhere near where they should be.

The swimming erratically could be a number of things but we need more info to be of any use.

 

[Colin_T]

Pictures and video of the fish?

What is the ammonia, nitrite, nitrate, pH and GH of the water (in numbers)?

How often do you do water changes and gravel cleans?

How long has the filter been running on the tank for?
When was the last time you cleaned the filter?