I have 8 Gallon fresh Water Tank with 7 Tiger Barb and 1 Blue Garumi . It is working from last 3 months. Water parameter are Ammonia zero, Nitrite zero and nitrate 40.

Fish are enjoying and going all good But I have some question. I have seen some green powder type in one corner of tank it is very less and same thing i found in filter when i took it out for cleaning. What it can be and how can I rid of it??

Another thing I want to know all fish are going good but 1 of my tiger barb is more fat and swimming vertically and he/she is also vibrating while swimming. But at only some time it is swimming okay Why is it so ??

Third question I have heard about some fish that eat dirt of the water and helps in filtration. What is that fish name and did it will be compatible with my tiger barb and is it worthful to add in my tank.

Sorry I ask lot question But I have some curiosities about all those thing so.

But Thanks to this forum as I learn from here only how to maintain good Aquarium