Very strange situation

[SaltyCaramelSauce]

Hello everyone, so I have quite the strange situation going on right now in my aquariums. Ill try to keep this as simple as possible.

I have 3 tanks, 2 x 40 gallon and 1 x 15 fluval flex. The 40s have been up and running for about 10 weeks and the parameter's are ph 8, ammonia 0, nitrite 0.1, nitrate 10 according to the fluval test kit. I added cherry shrimp 2 weeks ago and then i added 2 baby bristlenose plecos last week to each tank. All was going well until I added some MTS I ordered online and then the next morning all fish were dead but shrimp are fine. As of writing this, all shrimp are thriving and I even have a few berried. I did check parameters again and got same readings. Then I did 50% water change, checked parameters again and added 4 silver tip tetras. immediately I noticed some of the tetras flashing but then stopped. I watched them and all seemed fine. I woke this morning to all of them dead but all shrimp in the 40s are fine. 

Now whats crazy is the fluval flex which is only a couple of weeks old is running smooth and has 8 emerald tetras, 6 pygmy corys and a nerite snail. The only difference is no MTS. The MTS were black when i got them out of the mail but have since begun to get their normal color shells. 

Any thoughts and thanks for the help. 

[Guppysnail]

I’m so sorry for your loss. looking from your description it sounds like the MTS brought in a fast acting fish pathogen.  I would allow the tank to continue running fishless for a minimum of 30 days 60 to be safe. Most pathogenic organisms require a host and will die off without one. 
 

In the meantime run carbon and change every 2 weeks just in case it was a chemical pathogen that only affected fish. 

[SaltyCaramelSauce]

Thank you so much for your reply. I will leave it fishless for a couple of months and hopefully that does it. I've googled my brains out trying to figure out what could kill them so quickly without harming the shrimp but have had no success. I've just never seen anything kill fish so quickly. 

[Tanked]

I would contact the seller, just to see what they say.  They aren't likely to admit to a problem for liability reasons, but you never know.

A quick search doesn't come up with much information regarding black MTS.

What is really strange here is that there is another topic where the fish are alive but the snails and shrimp keep dying.

[nabokovfan87]

Very sorry for your loss.

By chance, did the water that the snails were in go directly into your tank?

[SaltyCaramelSauce]

Thanks for your reply. I added the snails to a bucket of tank water and then after a few hours I removed them with a net and added them to the tanks. I did reach out to the seller and he said he has never had any problems like that and no one else has ever said anything about it.