Hey guys I have a 30 gallon tank with 6 african cichlids...well used to have 6 african cichlids. Anyways the tank was cycled and everything was great for a few weeks, then I did a water change and did a bit of vacuuming of the sand/cichlid gravel mix and withing 48 hours all my fish were dead. I tested the water twice with no signs of amonia, nitrate or nitrite,the PH and water temp were perfect.
My dad told me that all the fish were swimming at the top as if feeding or gasping for air. All my water tests were fine so I tested the tap water and that was good as well.
Any idea what could have killed my fish?
how did you cycle this tank ??
it is odd there are no nitrates( I have seen that in a planted tanks)
I suspect either. pocket of toxic gas or some foreign chemical may have made it's way into the tank.