sudden pH drop???

So I am some what new to the saltwater community and I'm still having my ups and downs with my experiences. One of my recent downs, I was trying a new food in my nano 6 gallon, frozen Brine Shrimp. after feeding a half cube, and watching everyone eat things seemed fine. First thing I notice in the morning, dead fish, some puffy polyps and an extremely low pH. I cleaned up the dead, did a water change, and added a buffer. The pH returned to the norm around 8.0 and all other levels seemed fine and the polyps went back to normal. Talked with the LFS and they said it was not the food and have no idea what it could have been, maybe poor filtration. when I bought the frozen food I also purchased two fire fish gobies and added them to the tank. the only other live stock in there was a peppermint shrimp and some hermits and the polyps. I know nano's can sometimes be tricky and it doesn't take much to push them over the edge. Any ideas? I'm still clueless on this mystery.

I'm running an Eheim canister filter, so I don't think poor filtration mixed with the left over uneaten shrimp was an issue. (thats what the LFS guys think)

thanks for the help.

 

Its difficult to be 100% on the cause of death in many situations
but my opinion is

6 gallon tank how old is it?

and you added 2 x firefish
its possible that the tank was not ready for that much of an increase in bio load
and ammonia or nitrite spikes killed the fish and made the polyps look unhealthy


its also possible that with the additional demand on oxygen in there, from the 2 new fish
dropped the oxygen to unhealthy levels during the night and that the CO2 that would have been present, caused the PH to drop

whats your water flow like, surface agitation is important for good gas exhange and a more stable PH

Are you running a skimmer on there, as that can help with oxygenation and also removes a lot of protien before it breaks down and adds to the water quality issues

Steve

 

The tank is about 8 months fresh.

as far as flow, I have a mini Hydor jet in there, between that and the flow on the canister its good, should be. No skimmer, no room. the tank is a fluval edge so the opening is small and space is limited but its big enough to breath.

I thinking your right, maybe too much at once sort of thing and combined with the bit of brine shrimp left overs robbed the oxygen.

thanks Steve I'm taking everything into consideration for the future, I don't want to make this mistake again.

-Steven