Dont bother letting it hang around in the water all day.
Boil a kettle and add water in a buket to soak them in, after 30-60 mins, replace boiling water.
Do this 10-15 times.
Then start soaking them in luke warm water for 2 hours and check water colour
If its still colouring the water
Reapeat the boils
If the colouring is minimal, add them to the tank, the filter will absorb some and also water changing every week which youll have to do anyway will sort it out after a few weeks (Mine dont colour my tank at all, i only washed them down for 2 days with this method, though my tank is 240L, so its a lot of water, if you have a smaller tank its easier for them to colour)
