Emerald crabs keep dying

[oKrazyii]

I’ve now officially lost 2 emerald crabs the EXACT same way within a week of purchasing, like 2 days ago I walked into my room to see 1 on its back next to a rock twitching and then 2 days later he was dead, last night I saw my other emerald crab holding onto the side of a rock with only its back legs looking completely stiff, I moved my scrapper next to him to see if he’d move and no movement at all. Today I walk into my room and he’s fallen off the rock onto his back still absolutely no movement. I ordered a algae pack off reefcleaners yesterday that will come with 2 more emerald crabs and would like to figure out what is going on before they arrive and inevitably die, all other fish and inverts are doing fine including, 2 small Cortez hermit crabs, 2 bigger Halloween hermits, 2 nassrius snails, 3 nerite snails and roughly 9 cerith snails, a peppermint shrimp, a Clarkii clown and a firefin goby (I also have a pithos crab gotten the same day as the emeralds that i believe is still alive but he mostly hides under the sand so I’m not completely sure) ammonia nitrate and nitrite are all fine, temp is between 79 and 80, I’m running a uv sterilizer, carbon in my filter, and 2 circulation pumps for flow, I’m insanely confused as to what could be going on. Any help on what to check or test for would be very much appreciate as like I said I’m getting an all algae crew off reef cleaners and also added a 1 brittle star, 1 serpent star, and 1 pistol shrimp to the order and would really like to not lose anything.

 

[Harpo]

Please tell us about your water parameters

 

[oKrazyii]

Please tell us about your water parameters

Running api master test kit. Ammonia between .25 and 0, nitrite between .25 and 0 and nitrate between 20 and 10 (edited because I didn’t wait long enough on nitrate)

 

[BristleWormHater]

Running api master test kit. Ammonia between .25 and 0, nitrite between .25 and 0 and nitrate between 5.0 and 0

Calcium?

 

[Shirak]

No reason to run ammonia and nitrite testing in a cycled reef tank. So you can skip that. So first thing is with inverts like snails and crabs you get locally. Check salinity of the water they came from and your tank. If it's within a point then you are good to put them in. If it's off a couple points or more then you should acclimate them. These types of inverts don't adjust well to quick changes in salinity. Note that reef cleaners has their own set of protocols to handle shipped inverts so you should follow their directions.

Other thing is the possibility you are seeing a molt from the crab on the one that was attached to the rock? They look just like the crab and can be hard to tell if it is just the shell or not.

Picture with white light of the tank might help too. Is there enough food for them to eat? If there isn't then a week is about as long as they will last.

PS. This is not an emergency

 

[Goaway]

So what is your levels of
salinity
calcium
alk
ph

Do you know what the salinity of the green crabs were before you added them?

 

[oKrazyii]

Calcium?

Calcium is roughly 490, sorry only my second time testing calcium and the test is a little confusing lol

 

[oKrazyii]

So what is your levels of
salinity
calcium
alk
ph

Do you know what the salinity of the green crabs were before you added them?

I don’t think I have an alk test, will test salinity and ph in a few, not sure what the salinity of their tank was but I drip acclimated them for roughly an hr and a half after a 30min bag acclimation to get the temp right ( they were bought locally from my lfs but after a cleaning shrimp died 5mins into being dropped into my tank because I didn’t acclimate him right i take 0 chances)

 

[Fish Fan]

Crabs are some of the hardiest critters known, I don't think a small change in salinity is what's taking the OP's crabs out one by one (and I have seen the OP's previous posts).

Is it possible that copper or something else is getting in the tank?

@oKrazyii are you using tap water or RODI water?