I should add that they dislodge relatively easily from the leaves just by agitating with the tweezers and seem relatively buoyant as float around in the current easily before sinking.
This is a brand new build about 4 weeks old now. No fish or inverts (that I’ve added), no hard scape, new tropica soul and all tissue culture plants except for Ludwigia palustratis that I got as a new pot specimen. Only plant I can see affected is the Monte Carlo.
It has CO2 injection and fertiliser added weekly after 75% water changes.
