Symptoms of excessive Nitrate?

[StuG]

Yes, I spelled it correctly. I, in the last few days, have lost two Glofish (zebra Danio).
They acted as if they had swim bladder disease, except within hours of that starting they were dead.
Basically, they would start off kind of curled up and floating about the tank with no control (hence the swim bladder thought), and then just quit breathing.
I could see no other signs of distress, such as white marks, worms, fungus, pineconing, etc.
However, when I tested my tank water the pH was pretty high (7.8), and the Nitrates were above 40 ( I would guess 45-50).
I have of course now done a PWC & will test again tonight (PWC was done yesterday).
Anyway, could high Noitrates cause a death like that, or is there something else going on? Could it just be a bad batch of fish (they're about 2 months in my tank)?
Any help or pointers would certainly be appreciated.
Oh, and my Nitrite and Ammonia are both at 0.

 

[Floyd R Turbo]

I personally don't think 40-50 Nitrates are excessive. Elevated, yes. Shoot for below 40, 20 preferably. 7.8 pH is not that high. My tank is always right around there.

It just might have been their time.

What test kit are you using?

 

[BigJim]

Glofish are patented and breeders have to pay a royalty on each fish. This makes the fish expensive to cull, so weak and deformed fish that would have been removed normally aren't. It's very possible that this is the problem you're experiencing.

I like to keep my nitrates below 20ppm. Some LFSs will give you a hard time about replacing fish under warranty at 40ppm of nitrate, but I don't think it would be toxic to a healthy fish.

 

[StuG]

@Floyd. I'm using API liquid

I didn't know about the royalties on Glofish. I know how that stuff goes!
Well, ok, hopefully it was indeed just their time to go. I'll keep an eye out on the others. (3 left). Is there anything else I should be on the lookout for?

 

[BigJim]

Unfortunately, when people monkey with a species, the result is usually weaker than the natural variant. Glofish have a jellyfish gene spliced into their DNA. The original intent was to use them to test water quality. If the water was bad, the fish would glow. It didn't work out very well, but the result looks cool.

Just keep an eye on the rest of the fish. If you see specific symptoms, I'm sure someone here can help you out.