I think the coffee filter suggestion before storing is to remove fine metallic particles not caught by the magnet. Leaving the slime mold in the solution and then reusing it may end up covering the wheel surface with slime, not my preference. BradGE's solution could also help with humidifying your work area . I will try the algaecide. I have a pH meter and will do a before and after to see if it changes, but doubt that a product advertised as safe for animals to drink would do much to 2 liters of water.