fish always in the same spot, fast breathing, a little pale. Those arethe only symptoms. What can it be?

[bela]

I have plenty of fish (maybe too many) in my 40 gallon. Everyone is ok except this T.Ellioti I bought 10 days ago.

I bought 3 of them and the other two are also fine.

Ph is 7,5

26 degrees celsius.

I am sure there are no amonia, no nitrites. Actually I have not measure those, but if it that was the issue, other fish would also be in trouble, right?

Nitrates aorund 25ppm

GH 5 (I live in Madrid and our water is VERY soft).

Any clues?

Thanks

 

[H.K.Luterman]

I'd first make sure it isn't your water parameters via a water test just to check off that box. 

I'm not familiar with T.Ellioti (quick Google search says it's a South American cichlid). I'm assuming soft water is appropriate for it?

Could it be getting bullied by any of the other inhabitants?

Another possibility is gill flukes, which causes respiration issues, but I would make sure all the "simple" answers are checked first before trying medication. 

[Colu]

I agree with @H.K.LutermanFrist check your ammonia and nitirte before anything else just because this fish is the only one showing symptoms doesn't it not a water quality as he could be the weakest individual in the group