First off, I just inherited the tank (and it's problems) and am just learning. Saturday night the fish feeder dumped in way too much food. I scooped a lot of it out but some of it floated to the bottom. The fish seemed well and healthy. The next morning I had 3 dead fish at the bottom and the 2 left were struggling near the top. I saved the 2 left. What happened? Could the food have caused that? Did the water go toxic because if the food?
First off I changed 65% of the water about 9 days prior to that disaster, as well as a filter cleaning (fluval 306), when I first got the aquarium. So I wasn't expecting water to go bad so soon in an established tank. My tank is 45 gallons with some anubias plants and major black beard algae. I am just learning about testing the water. The water that the fish died in I did do a nitrate test after and it was high, about 110ppm+. I didn't do any other tests.
Then I changed almost all of the water and scrubbed off a lot of the algae from things and plants The nitrates went down to 20 ppm. And today I tested it at less than 5ppm. Today I also tested ammonia at zero, nitrite at zero.
The other thing is I threw out the fish food that was in the feeder during the panic thinking it was bad. Now the remaining fish just spit out the food I bought. Don't know what they ate before but it was also a flake food. Do they just not like the food? Or are they stressed? They used to eat the other food like crazy. Now, they go for the food but spit it out.