Grey At Night, Black In The Daylight

Whats up yall,
My rainbow shark has been changing color and acting very relaxed lately. During the daytime, he turns black and just kinda hangs out in the castle in my tank (which I put there just for him), but in the morning and evening, he turns grey and is pretty active. Are these fish nocturnal? Water conditions are fine, the tank is certainly not overstocked, its cycled, etc - all conditions are nominal.

I did two small water changes last week over the course of three days in an attempt to bring the nitrates down, as well as replaced the filter cartridge (it was like 4 months old). No other fish in the tank have shown any change in behavior.

I appreciate any feedback. Cheers!
-J

 

When you say replaced the filter cartridge.. did you have another one behind it to collect beneficial bacteria?? You may have lost your cycle..??

 

Sounds like normal behavior to me. Mine was like that too.
Also, I agree with the above. I personally don't change my filter cartridges.

 

I did place a fresh cartridge in the tank a few days before replacing the old one. I just dropped it right in. I had already read of the risks of changing the cartridge cold, and I put it off for as long as I could, but the old cartridge was starting to disintegrate. I checked the water immediately after the change, and the next day, and everything was copacetic.

Thanks for you replies! I really appreciate how helpful and friendly this community is.
-J

 

I did place a fresh cartridge in the tank a few days before replacing the old one. I just dropped it right in. I had already read of the risks of changing the cartridge cold, and I put it off for as long as I could, but the old cartridge was starting to disintegrate. I checked the water immediately after the change, and the next day, and everything was copacetic.

Thanks for you replies! I really appreciate how helpful and friendly this community is.
-J

Ok that's great!!