Not sure what happened. Tested my water the other night. Everything was good. P.h. 7.4, ammonia 0, nitrites a trace, nitrates 20. Came home the next day to a dead pleco, red tail shark, 2 dead snails, and a dead african dwarf frog. cleaned them out..had a funeral, and checked my levels again. Ph was the same, ammonia was the same, but the other 2 spiked like crazy. Nitrites went to 2 ppm, and nitrates went to over the max on an api test kit (160). Did an immediate water change. levels were better, then did another water change this morning. levels are normal now, and I'll do another tomorrow. What in gods creation would cause that??? ammonia didnt move, ph didnt move, but everything else shot way the heck up. Nothing has changed in 2 weeks in the tank. normal water changes on sunday, and nothing during the week. 2 weeks ago I did change the tank around, removed the substrate, put in sand instead, and added coral (1 big chunk about 6 inches across, same height), after it was cleaned like crazy with nothing but water), but Id think if there was going ot be a change it would happen in the first few days...not 2 weeks later.

WTH?!?!?!?

and tonight I lost 2 balas, and a snail...what the heck...my levels are perfect right now...I don't know what's going on. What else can I test for to get myself an answer?

you mentioned coral. is this a freshwater or marine tank?

Freshwater, but it's not a live coral, wasn't live when I received it. It sat for days at my house (dry) I washed it, let it sit dry, washed it. Repeated about 5 times to make sure it was completely clean, and put it in the tank. was in there about 2 weeks before the fish die off. Haven't lost any since the balas, but I'm still confused.

This is the coral
https://www.chewy.com/natures-ocean-...rium/dp/167758

looks like base rock used in marine systems. Let us know how it works.

actually it could have been the base rock. Maybe some kind of obscure toxin leached out.


But that's just a guess.