Dying fish, help.........

[Smokejumper]

Hi, I have a marine tank with 2 x damsels, 1 x clown, and a wrasse. I set this tank up just over 6 months ago and I have lost a shrimp, Clown fish, Soft corals and even a sea urchin. Ive treated the water twice for bacteria and all chemical levels (Salt, nitrates etc) are all within normal limits. Temperature is fine too, so what could be killing my fish? The water looks clean too and I have the correct pump and heater for the size tank. I rotate 20% water with RO every 10 days too

. Any ideas will be greatly appreciated, I attach some pics for help?? Thanks everyone.....

 

[florida joe]

what did you treat the tank with

 

[Smokejumper]

what did you treat the tank with

I am in the Uk and the local aquarium shop gave me something to combat a possible bacterial contamination. Unfortunately they cannot test the water for bacteria and all my other levels were fine

 

[florida joe]

So they gave you a broad spectrum anitbiotic