@vegetato I couldn’t get hold of Hydroguard sold out everywhere so got Great White, is that alright?
Did you get the powder or the liquid (Orca)?
The powder one is all they had.
That’s a bit trickier to use, the liquid version of that (Orca) is a more precise, less hazardous to handle (should wear a mask with powder, avoid kicking up dust, cleanup area well afterward), and less mess (FYI).
When I’ve used it (recently) the process was to add 1/8th of a gram or less to 20-50mL of water and then stir/mix it really well and then dump into the reservoir.
It helps to let the sediment settle and then pour it carefully to avoid dumping the “gunk” into the reservoir, or use a syringe or pipette to extract from the top of the mixed solution.