Hello everyone, this is my first time posting here:;hi1. I have a 10 g tank that has been up and running since February. I started with 3 silvertip tetras, and 5 danios. After it was cycled I added 2 guppies but was advised to wait on any others until the tank was running for at least 3 months. Last month I added 4 panda coreys. Everything was running smoothly, all water tests were coming up good. So early last week after talking to a few different people from the pet store they told me I should be ok to add a Betta and some cardinal tetras. I was concerned about it being overstocked but they said as long as I was good with the water changes everything should be ok. It started the first night after I added those fish... I lost a cardinal. I also noticed a grey spot on another one, so I bagged him up and took him in to see if they knew what that was. They thought it may be fungal so advised me to treat the tank with Pimafix. I started the treatment but soon lost another cardinal and also the Betta . I tested the water again and the Nitrates were off the charts! So I started doing 20% water changes every other day. I also moved the panda coreys (I made this decision after I lost one of those as well) into my new 26 g tank that has been running for 4 weeks with danios. I have done 5 water changes since the nitrate spike and it is still off the charts!! I don't understand what is going on or what to do to fix the problem. Also 2 of the silvertip tetras have developed something funky as well. It isn't Ich but one has a big white (looks like a pimple) spot near his tail and another one has one on his mouth. I have already ran the Pimafix treatment for 7 days and they are still there. I do have a picture of it if that would be helpful. Any advice would be appreciated.. feeling really defeated here.