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.

The very light weight pumice rocks, which are lava rocks, contain a lot of hydrogen sulfide in the sealed up cells. You can smell it when you scrape the rock to break some of the glassy cells. That might be a problem if you have that kind of rocks - I think they float, so you would certainly know if you have them. Other than that I don't know of anything toxic about lava rocks.

Rocks that look like lava rocks? I'm not sure what that would be. Perhaps it is coal slag?

I'm not sure you would be able to measure the amount of ammonia or nitrites that could cause fish deaths. I haven't read anything about that as far as I can remember.

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.

CO2/Excel etc was dosed?

If you remove a lot of material, do a massive uprooting, clean asap and doing more than 60% is okay, as long as you normally do large water changes.

If it's a lower tech non CO2 method..........then this can cause issues, the tap and the tank water is much more different.

so slow refilling could resolve that issue.............

Regards,
Tom Barr

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.

Do you only observe this at night? Early morning? Maybe the surface movement is still not enough for the livestock? I would think that things hanging near the surface of the water would mean something specific.

Good luck.

-Mike B-

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.