Is something wrong?

[Gauge]

If you've read my posts in the past, you know my tank is historically a disaster. However, for the last two weeks I've only one fish, and it was to fin rot (which isn't what usually kills my fish). I've got a small amount of nitrite in my tank (0.1 or so). The question isn't about the dead fish, it's about the dead crabs. I've lost an arrow crab who I had for 4 months (an eternity in my tank) and a decorator crab I had for about a week. I lost both within the last two weeks or so.

I doubt this is relevant, but I also have the following inverts...
1 anemone crab
1 emerald crab
2 blue leg reef hermit crabs
1 red bali starfish
1 tiger tail sea cucumber

Now, I'm not wanting to know if the nitrites can kill the crabs. What I'm wanting to know is if there is anything else I should be looking for that would only kill crabs, not fish. Something perhaps I haven't thought to test for in the past or something like that.

 

[Pacu Man]

ive just started to get into crabs myself and i dont know if this is a case but a crab such as that emerald can be aggressive towards smaller crabs and might kill them and especially that anemone crab might be protecting its host from other crabs.

 

[stresco]

Nitrites will kill inverts. So will Nitrates, Copper, Low or High SG, Heat, Cold, Stray Voltage, Amonia, Low or High PH, and whole, whole lot of other things.

 

[Gauge]

Nitrites, as I said, are up a bit. If they're the culprit, that's fine. They're coming back down and will be zero before the replacement crab hits the water.

Nitrates are zero.

SG is 1.022

PH is a beautiful 8.2 (in the morning more like 8.1)

Ammonia is 0.

Temp stays at 79-80.

Both these crabs were the biggest and meanest crabs in the tank. It was quite clear that the arrow crab died of something other than stress. The decorator crab was twice the size of any crab in the tank.

Copper I haven't tested, but I don't think there's any source of it in the tank. I have a test, though, so I'll use it when I get home.

I don't know about stray voltage. I doubt that's it, though. All my pumps are 4 months old, and so was one of the crabs. You'd think he'd die pretty quickly or not at all.


Any other ideas? There are a lot of things that you can test for, and I have no idea what they all do when they are too high/low (i.e. magnesium, calcium, phosphate, etc, etc).

 

[kidafius]

Personally, IME, the emerald crab is the most dangerous "reef safe" crab there is, and I don't think that they should be in reef tanks. Mine has eaten parts of my starfish, mushrooms, and I have no doubt that yours is up to shenanigans. When I do my 55 to 120 change over, my emerals are going into the refugium area of my sump.

But, as Stresco has stated, there are lots of things. Nitrite is dangerous in very low amounts, but "they" say that <.3 is the "safe zone". It still could be the killer of the crabs. But usually, unless you see something die, they are tore up before you see them, especially with the emeralds and hermits.

 

[Hara]

it could also be that the bad tank conditions have just taken their toll. Something that is alive, can only take so much before finally succumbing. Even after the conditions improve.