lost 2 tangs with no sign of disease or injury

[axsalt]

I have a 90 gallon tank with live rock & live sand - probably 30-40lbs of rock. I have a wet/dry filter with a uv sterilizer. tank is approx 1 year old with 1 clown fish, a picasso trigger, porcupine puffer & 2 naso (1 blonde) tangs. Recently I noticed the tang not swimming properly and staying near the bottom of the tank. Finally rested on the substrate & ultimately dying. I checked my water parameters & all is well ph, ammonia, etc - nitrates were a little higher than usual but nothing to worry about. Any ideas - 2 tangs in 2 weeks gone. All other fish are fine. no signs of any disease or stress...

 

[beth]

My own exp with this is that tangs really have no or at least little tolerance for nitrates. Wet/Drys do create nitrate problems. What kind of substrate do you have? What is your nitrate level? What were you feeding the tangs? What size is your tank? Were the tangs aggressive with one another?

 

[axsalt]

Thanks for replying so fast.
The blonde was smaller than the naso by about 2 inches. The larger tang was about 5-6 inches.
The substrate is live sand.
The tangs were not aggressive with each other.
I was concerned it may be velvet or something.....
Oh, nitrate level at: 20-40

 

[beth]

So were these tangs new to the tank? I have to say that tangs really don't have much tolerance for nitrates. Was there any sign of malnutrition? HLLE? The fact that they both died at the same time makes me wonder if they did not have a fight when you were not looking. When tangs fight they use their swords. These are like knives. A cut is frequently lethal. However, the cut is so sharp and fine, it could go unnoticed by the hobbyist.

 

[axsalt]

Hey,
No fight...they died a week apart or so. maybe more. I had them for over 4 months. just strange the way they just got real slow, making they're way to the bottom then finally dying. Looked as if they were struggling to breathe perhaps.

 

[beth]

How did they look before this happened? How was there weight and color?

 

[axsalt]

No signs of anything at all.....just slow moving & not eating. Weird.

 

[mugs]

Sounds like the nitrates are a bit high and could have built up toxicity levels over a period of time. Not sure if that's enough time, but know they're not as tolerant as other species. Just my opinion.