before my hubby went to sleep last nite.he went to look at our favorite fish the arowana on the balcony.he yelled for me saying the fish is dead.i though it was another of his dumb joke as he knows i love this bugger to bits. feeling something was really wrong as he kept calling me i rushed to the tank and to my horror 2 tinfoil barbs and 15 feeder koi were dead in the tank.
only my arowana, pleco and a single ghost shrimp was alive.the water was reaking with dead fish smell.wish he hadn't closed the curtains yesterday
got a huge extra quality garbage bag meant for the arowana in case of an emergency and re homed him in another 90 gallon that was left running with a single climbing perch and a handful of ghost shrimp in it. scooped out all the dead fish and did a 100% water change which included the filter. didn't use water from that tank but the spare one. all the dead feeders had a black spot covering the whole of their chest cavity. even the tin foil had blood streaks in the same area and some of the feeders were on the glass and floor in the same area. don't know what went wrong in there but i was definitely not water issues. ammonia and nitrite was high but thats because the tank had dead decomposing fish in there so the water readings aren't dependable. i'm thinking electric shock but the aro and the plec are alive
only 100% of the smaller fishes are dead..what could have caused this?