Danios - two situations
We have a 20 gallon freshwater planted tank that we set up 8 months ago. We currently have 6 zebra danios, 1 dwarf gourami, 2 emerald corys, and 1 dwarf clown plecco.
On last check our water readings were fine, we are going to check it again this evening. We do weekly 1/3 water changes. We have two aquaclear30 filters running.
About 4 weeks ago we lost a gourami out of the blue and around the same time we noticed a female danio acting erratically. She was sitting in a plant and then would swim very quickly almost out of control around the plant and then settle again. She always comes up for food and sometimes interacts with other danios but often swims erratically and hides on the bottom. We had our water parameters checked and they were fine.
We then added 3 new danios as the recommended numbers were 6 in a tank and we didn't want any extra attention on the 'sick' danio. They adapted well in the tank, until yesterday one of the new danios has a large red fin. Originally we thought it was feces but it's location and thickness make more sense to be a fin. He is swimming more slowly and breathing heavier than the others but is eating and still interacting with others. Today his fin is not red, but looks abnormal. One side is big and thick and the other is almost a doublet. We didn't notice this before but perhaps he was born with it? It won't let me add a picture but I will keep trying.
I'd appreciate any feedback! We love our fish and are new to keeping a tank.