I do a 10% water change weekly and a 20% water change monthly on the 1st, i set my water out for 48 hr. before any changes. Up to this tank I have always had 10 gal, which i never had any trouble out of, but wanted a big variety of fish. On August 1 my water levels with Master Kit (New KIT Expiration 12/25)was as follows:
Water Temp: 78-80 Degrees
PH: 7.6
HPH: 7.4
Amon: 0
Nitrite: 0
Nitrate: 0
That night (August 1st) my Green Killing Machine Tube went out and got up next morning 90% of my fish was dead. of the remaining 5 that was left one more died yesterday. I don't think the Green Killing Machine is the issue, because this is not the 1st fish kill that i have had with this tank. This makes about the 5th, each time following a 20% or better water change. I only have Tetras in this tank. And I understand that fish get sick, but not after water changes.
On August 22 I did water test for copper, the results as follows:
Hardness: 0
Chorine: 0
Alka: 6
Nitrite: 0
Nitrate: 10
Iron: 0
Copper: 0
If I cant find a solution, then when i get down to the last 2 or 3 fish, I'm going to transfer them to my extra Betta Tank and get rid of this demon tank. I haven't done anymore water changes but have added water, about 2 gallons a week. It seems that the tank thrives with less changes.