Answer:
3750 hours
Step-by-step explanation:
Its a bit of a stretch to call this a biology question, nonetheless
Volume - 15 x 25 x 30 = 11, 250 m³
Total water in full tank = 11, 250 m³ x 1000 L = 11, 250, 000 L
Complete cycle = 11, 250, 000 L/3000 L = 3750 hours