Everything was going so well. Ive had my tank for about 7 odd months. I had 20 rummy nose tetra, 20 cardinal tetra, 5 white fin tetra, 6 plecos, 3 bristlenose catfish, 4 guppies, and 10 cherry barbs (5m/5f). On Sunday of those fish I added 10 cardinals, 4 guppies and the white fins. The female cherry barbs killed all the guppies except 1 within 1 day of putting them in the tank. The one remaining now sits at the top of the tank and doesn't move around too much. Now a day later I have 2 dead cherry barbs (1m/1f) and some very dodgy looking cardinals, and all the rummy noses tetras have lost colour. I got the dead fish out and did a 30% water change and re-checked levels and they were the same as they have always been.
I don't have a quarantine tank. Is this a store issue? I only get my fish from one store and it is supposed to be the best in the city. Please help what do I do. Am I going to loose all my fish?
Tank parameters
size - 850L
Hardscape
Temp - 26 deg C
pH - 6.6
Ammonia - approx 0.05-0.1
Nitrite - 0
Nitrate - approx 3 ppm
These are taken by freshwater master kit and is a colour chart hence the approx.

I don't have a quarantine tank. Is this a store issue? I only get my fish from one store and it is supposed to be the best in the city. Please help what do I do. Am I going to loose all my fish?
Tank parameters
size - 850L
Hardscape
Temp - 26 deg C
pH - 6.6
Ammonia - approx 0.05-0.1
Nitrite - 0
Nitrate - approx 3 ppm
These are taken by freshwater master kit and is a colour chart hence the approx.



