The mysterious shrimp and crab killing aquarium

[friendlyAlien]

Hi,

I am looking for some ideas ... over the last few months all my shrip and hermits died. Also my brittle start died. Clams and corals seem to be happy and so are the cukes and the fish.

All standard water tests look good (kh, ph, ca, iodine, dissolved org, Nitrite, Nitrate, temp)

I did a lot of water changes and reintroduced them just to never see them again after the first night.

Before I restock again, anyone an idea what could be the cause of this mass killing?

Thanks,
Carsten

[moriartiholmes]

Sounds like a predator. It could be a number of different ones. Do you have any fish that sleep on the substrate at night? A lot of those predators will go after sleeping fish as well.
If you really want to know, you could go fishing. You could place a crab in a glass jar that the predator can swim/crawl etc into but not out of. By the next day, you should have it out, or be designing the next trap.

[nwrogers]

Could it be a Mantis Shrimp? Are all of the empty shells in one location?

[chrisguy]

Could be copper. Is the tank new? If it's used did the prior owner use Copper medication (or did you) to treat a disease?

There was a huge article a little while back in the chem forum just like this and in the end it was copper from a small DIY part that was killing shrimp and snails.

[m-fine]

Could be daily temperature, PH or salinity swings. Copper is defintiely a good possibility.

Do you have snails and are they OK?

[moriartiholmes]

Copper sounds interesting. Temp fluxes could be it too. But the other sensitive life is fine and it sounds like your not finding all the remains... I would set a trap and see if you catch anything. For copper, good carbon use might help. Also you can test for it, but I'm not sure how good the tests are. How are u acclimating them? These are all pretty sensitive animals.

[friendlyAlien]

alright, I tested for copper but no success. I never used copper so it was doubtful unless it came through my 4 stage RODI unit.

Temp flux is possible it is going from 78.5 at night to 81.4 during the day.

PH was 8.0 this morning and 8.2 last night.

Acclimation I do with a 45 min drip acclimation into a container that is swimming in the sump (which is keeping the temperature stable).

I did try a a big carbon bag after the first water test before adding the shrimp and crabs

As for snails - yes - thousands (literally) of them, they successfully breed all the time and I have them in all sizes - need some?

[friendlyAlien]

I will try to setup the trap ... that is a good idea.