Mysterious deaths of fish and plants looking terrible
My Dad has tried to join me in my love of aquariums and has had a 40g freshwater tank set up for 2 years. He had about (3) Gouramis, about (7) very small Tetras, and a few bottom feeders. Overstocked a bit, but I gotta say they were thriving for about 18 months.
It's also a beautifully planted aquarium.
A few months ago his plants started looking terrible, and he lost (3) fish. The plants eventually sprung back to life.
All of a sudden his plants seemed to start to look awful again, and he's had another rash of fish deaths. He lost about (6) fish over the last week, and there are a couple others that don't seem to be eating.
We tested for all of the basics. pH he keeps around 6.7 using a CO2 tank, Ammonia is 0, Nitrites are 0, Nitrates are in an acceptable range. Temperature is around 76-77.
I don't remember what his lighting is, but it's sufficent, and wouldn't have an affect on the fish deaths anyway.
Should he be worried that something is suddenly in his municipal tap water that he hasn't tested for?
He changes 50% of the water each week because it's right next to a sink and easy to do. He's going to scale back to a normal 20% and start using a stresscoat.
He doesn't clean the tank glass with anything but a wet cloth, so he's not getting any cleaner in the tank.