Dead fish and shrimp please help!

Is there any rock that looks like lava rock that is not suitable for the aquarium?

Yesterday I pulled out a large crypt from my 75 gallon tank. This stirred up the subtrate a good bit due to the extensive root system. I did about a 60% water change immediately after. I also added some lava rock I puchased from my LFS. I used Kordon Amquel for a dechlorinator because I ran out of seachem prime and my LFS carries Amquel.

Any way all was well until this morning I woke up to a dead flying fox and about 4 dead shrimp. All my snails were heading to the top of the tank. I tested for ammonia thinking disturbing the substrate may be the culprit but there was next to none. Certainly not a level that would harm my fish or shrimp. I did another emergency water change. This afternoon there were more dead shrimp and the fish snails and shrimp gasping at the top of the tank. I did another water change. Tonight same deal some dead shrimp and from the looks of it soon to be dead tetras and everyone up top. I finally pulled the lava rock out but I am out of dechlorinator again so I can't do a WC. I have a powerhead rippling the top of the water for aeration. The filter appears to be working fine. What in the world could be going on? Did I get some seriously bad lava rock.

What in the world could be so toxic to still be a problem through 3 water changes and in a heavily planted tank.

I am assuming much of my livestock is doomed. Luckily I only had a few fish in there. A lotta cherries though. It's a shame.

 

Well I took out the lava rock and all is well this morning. I have no idea why they caused this. Luckily all the remaining fish and shrimp including the tetras survived.

Vaughn, the rocks sink just fine and don't seem to have any odor to them. I will try to boil the rocks and try them again and observe closely to look for any signs of stress. The snails usually hit the top of the tank long before the fish do.

I'll admit I didn't clean the rocks well to begin with. Call it cockiness because I have had terrific luck with my tank as far as fish health and with adding things like rocks and driftwood. That is except for my recent flood issue I learned my lesson now though. Too bad it took the lives of a few shrimp and a flying fox to teach it.

Cleaning the rocks may not have helped in the first place. We'll see this coming weekend. I'm gonna have to talk to the guy at my LFS and at least let him know what happened so other people can be aware.

 

I dose excel. I usually do about a 60% change weekly. I had thought taking out the lava rock helped and it did for a short time but for some odd reason again tonight my shrimp are back on top of the water. I am seriously confused. I can't do anything until tommorrow. My Seachem Prime should finally be here.

 

Well I got my Prime in, boiled my rocks, did a WC and reintroduced the lava rocks and everything is as it should be now. Fish and shrimp are happy. Amquel either doesn't even come close to seachem prime at removing chlorine, chloramines and ammonia, or there was something on the rocks. Those are really the only 2 changes. I guess I'll be sure to clean everything very well, and never run out of prime again.