My Chubby Green Spotted Puffer
New member here and glad to meet with all the "puffers lovers" here. Very quickly I will share my background in points:
I got this chubby puffer since 1.5 years ago when he was a youngster. He is always a big eater, his belly is so big it looks like it will explode any moment (I wish I could upload his pic). Now he is almost 2 inches in length. Very healthy. I have three other smaller puffers, same sizes, all currently have white spot on skins and some area it looks like the skin is damaged. Finally, one more baby puffer just passed away due to same skin issue.
Tank condition: Juwel Rio125 tank, brackish water with 1.005 salinity, just yesterday I made it 1.010 (Not sure if this is too high). PH over 7.6, No3 got down from 100mg/l to 25mg/l recently after a few water changes (25-30% each time). Sand at tank bottom. My tank also have three other types of fishes which lived with the puffers for the last full year. They never fight or anything except chasing their own kind.
Recent issue: Just a quick sharing, while I thought my big puffer is the kindness ever, I started to realized he chased the small puffers at night. But he never bothers with other fishes. About the white skin issue, I have no idea what is that, I had tried many ways and even Paraguard would help it little but as soon as the solution is finished, the white spot is back.
My previous routine is only change 15% of water when I cleaned up the tank once every week. And my fishes are very healthy until the white skin issue came up. So someone adviced me if I do not add new water, it is like a bucket of poo water circulating the tank. This might be one of the reasons why my fishes are affected. So I changed water a little more frequently. Then last few days, two types of fishes (Total 6 of them) died suddenly last two days. They were very healthy before.
And all my puffers only eats a little now. I don't know what to do, how to cure the white skin issue with the three puffers. Can someone advice me what to do? And what did I do wrong?
Should I lower the salinity or anything? What about my PH?
One more recent changed I did is to add a piece of Chinese plant kind roots in the water. The tank did become a little yellowish which I removed it now.