Katya is slowly working on the sea-water fish tank.
She had bought a water purifying apparatus, and today, I connected it with a water tap.
I slowly passed 20 litters of water from the tap in order to take out extra powders of activated charcoal.
It took nearly two hours to eliminate charcoal powders.
Tomorrow, I will run the instrument for two hours. After that, we should be able to obtain pure water for ocean fish.