Urchins and Nitrates

[Gtinnel]

I've always heard that higher nitrates are hard on an urchin and can cause it to drops spines or even kill it, but will a sudden change of nitrate do the same?

I have (well had) a Pincushion Urchin in my refugium for probably over a year. It started in my display but I got tired of it constantly moving frags on me so I moved it into my refugium, where it quickly ate all of my macro algea. Once the macro algea was gone I left the lights on to grow algea in there for a food source for the urchin, which seemed to be working well until a few days ago. I've never had high nitrates in my tank, actually I've always had to dose to keep nitrates up. Normally once they drop to about 2 I dose them back up to close to 5. Late last week I let them drop to 1.6 and I added a little too much nitrate solution and raised it up to 6.8. A few days ago I noticed the urchin was dead. Would a instant swing of 5.2ppm of nitrate potentially kill an urchin? Nothing else in the tank seemed to be effected by the slightly larger swing than normal though. I'm actually fairly glad that it's no longer in my fuge, so that I can now add chaeto if I ever decide I need to, but I'm just curious what could've killed it.

 

[homer1475]

My nitrates range from 10 to 20 depending on when I do a WC. I have 2 tuxedo's and short spine pincushion. None are effected by the higher end of the scale, or the rapid decline when I do a WC.

 

[Gtinnel]

My nitrates range from 10 to 20 depending on when I do a WC. I have 2 tuxedo's and short spine pincushion. None are effected by the higher end of the scale, or the rapid decline when I do a WC.

I have no idea what high range is considered harmful to them, all I've ever read was that elevated nitrate is harmful, I've never seen a specific value quoted.
I wonder if a sudden swing is hard on them is it equally hard going from high to low or low to high?
It likely could be that I was wrong that the nuisance algea growing in my refugium was a sufficient food source, and it eventually starved to death.

 

[homer1475]

I honestly thought they ate more coralline then algae? I could be wrong too, but I know my 3 absolutely LOVE coralline and eat that way before the algae.

 

[Gtinnel]

I honestly thought they ate more coralline then algae? I could be wrong too, but I know my 3 absolutely LOVE coralline and eat that way before the algae.

I know they do eat coralline but I also know once I put him in my refugium the chaeto was gone really quickly. Of course looking back at it my nitrates were always low so I'm sure my chaeto wasn't doing well to start with, I'm not sure if chaeto just disintegrates but if so that could've been what happened to it.

 

[blaxsun]

They seem to love corraline algae.

 

[Cory]

I dont think no3 levels would kill an urchin. My two decorator urchins live in 50ppm no3 waters or more and are thriving. Most likely would die from food or heavy metals. Mine occasionally get algse pellets i feed the fish.