I have seen some folks that are concerned in re visible microbubbles that show up with high turbulence states, like when adding water with a python. If that has any proven negative effect other than cosmetic I am unaware. The other definition of microbubbles is when gasses come out of solution inside of the microvasculature of the fish and can often be seen in the arterioles on the tail and pectoral fins. Depending on the size of the bubble it can cause significant ischemic tissue damage. This is caused due to supersaturation of a gas, often CO2 that then off-gasses if you store your water in the storage container or occasionally in your fish if you do not. Also remember that the partial pressure of a gas in solution increases with increasing temperature, meaning all gasses (primarily O2 N2, and CO2) that are dissolved in a liquid will come out of solution as the liquid warms, pressure also increases the saturation point of a dissolved gas. If your pH increases with storage that is a good indicator that you have some CO2 coming out of solution. https://fishhistopathology.com/home/...ubble-disease/