Afish is removed from a contaminated lake. you determine that a particular toxin (x) is present in its cells at concentration x = 1,500 μg/l. you place the fish in a tank full of clean water (x = 0 μg/l), and measure the toxin concentration in the fish cells each day for the next 10 days.

after making your hypothesis, you test it by measuring the toxin levels in the fish at various times during its 10 days in the tank. you observe that the level of toxin in the fish drops from 1,500 μg/l to 750 μg/l and then stabilizes at 750 μg/l. you test the water in the tank and find that after it stabilizes, toxin is present in the water at concentration 750 μg/l also. what can you do to continue to reduce the toxin level in the fish below 750 μg/l?