crustaceans dying

[hagfish]

About a month ago I had a fire shrimp die. Then a week or two after that, an emerald crab died. Now tonight I have a skunk shrimp that is not yet dead, but is laying on his back and not looking good. He has not been eating for about a week. I do have about 6 hermit crabs that appear to be fine. They have all been in since near the beginning (about 2 1/2) months ago. I also have a porcelain crab and 3 snails which are fine.
This is a 20 gallon tank. Ammonia, and nitrite have both been zero throughout this whole time. Nitrate was about 80 when the fire shrimp died, but I have had it at 10 or less since shortly after that. My specific gravity was about 21 toward the beginning. Then I had gradually gotten it to 23 or so. Then in the last week I had taken it back down to 20 or 21. I feel this may be a problem. I used some Melafix to try to treat some infections a fish had, but it claims to be reef/invert safe. I have not tested for copper, but plan to do so tomorrow. Anybody have any ideas what could be wrong here?:help: :notsure:

 

[montidanae]

good idea on the copper test im leaning thats thats the reason of death.

 

[hagfish]

That's all I can think of. But if it's there, then how could it get in there? And is there any way to get rid of it?
I'll get run the copper test tomorrow and post the result.

 

[big911dog]

also dont forget that SG is affected by temperature. what r u measuring with? if a swing arm, maybe its not functioning properly.
if possible, have ur LFS double check ur parameters.
hth....

 

[hagfish]

Temp has been pretty consistent at about 76-79. I have been using a swing arm hydrometer and a floating hydrometer/thermometer.
I had started out using tap water with chlorine remover (stress coat). But I have been using distilled water for the last few weeks.

 

[nero]

hmm... your temp sounds a bit low... i would try to raise it to about 80-82 degrees. that might be your problem if everything else sounds fine.

 

[bang guy]

Originally posted by hagfish
I had started out using tap water
That could be a source of Copper. I'm not saying that that's the reason though.
How are your snails doing?
If only Crustaceans are affected I would point to an Iodine overdose.
* - edit * I just saw that your snails are fine. Are you doing regular water changes? Are you dosing anything?

 

[hagfish]

I have 3 snails right now. One was the first creature in the tank. They all seem fine. Although I did lose one just a few days after putting him in there. That was about a month ago.
I have been changing out about 10% of the water once a week. I also did 2 larger changes of 20% or so.
The only other things I have added to the tank is some stress coat to remove the chlorine in the beginning and some melafix.
If iodine is the problem, and I haven't been adding iodine, could it be my salt mix having inconsistencies in iodine?
I'm going to go buy that copper test kit in just a few.

 

[bang guy]

It's well documented that salt mix has too much Iodine but not enough to kill that fast. Nori is another big source as well as any fish food containing whole crustaceans.
Generally if you're not adding Iodine you'll still have relatively high levels but not high enough to kill.

 

[hagfish]

Well, I bought the copper test and it is coming up with zero.
Bang, you mentioned feeding whole crustaceans. I usually feed frozen brine shimp once a day. Is that a potential problem? I also feed flake food occasionally.
Since the copper test is coming up with zero, any ideas what I should look for next? Stick with the iodine theory maybe? I'm just wondering where it would come from? Food maybe?
Also, is it strange that I've had red leg hermits in the tank longer than just about anything and they are still OK?
Oh, Bang, what is Nori? A type of food I assume.

 

[bang guy]

To be honest I don't think the Iodine theory holds water because your waterchange frequency is enough to bring down high Iodine levels.
Snails would be affected first if it were copper.
Your Salinity is running 30 - 31ppt based on your S.G. and temp. It should be above 35ppt IMO but you're still not low enough to kill that fast.
How often do you topoff evaporated water?

 

[hagfish]

I had been topping off once or twice a week. But lately I've been trying to shoot for about every other day.

 

[big911dog]

nori is an algea based product which comes in sheets. its for feeding herbivores. it also wraps yummi sushi!

 

[hagfish]

bump.
I'm still not sure what's killing my crabs/shrimp. Bang, do you think I should just try increasing the salinity a bit and make sure I keep it steady and try again? Or could there be something else wrong?

 

[bang guy]

The Salinity would have been stress but I don't think it was low enough to kill them. I'm all out of ideas. Sorry

 

[hagfish]

Well, I've still got a porcelain crab in there so I suppose I can measure my current success with him. Although he's very difficult to see since he hides all the time. Maybe my losses can just be chalked up as a beginner taking some lumps I suppose.
BTW, how did you get the salinity calculation based on SG and temp?

 

[big911dog]

i've seen charts for salinity/temp conversions in some newbie books. have u thought about a refractometer? they're about $50 for one with automatic temp conversion. great investment IMO.
Good luck!