1. **State the problem:** We have a rectangular fish tank with a bottom area of 450 inches² and it is filled with water to a height of 10 inches. We need to find the volume of water in the tank in cubic inches. 2. **Formula used:** The volume $V$ of a rectangular prism (tank) is given by the formula: $$V = \text{base area} \times \text{height}$$ 3. **Apply the formula:** Here, the base area is 450 inches² and the height of the water is 10 inches. 4. **Calculate the volume:** $$V = 450 \times 10$$ 5. **Simplify:** $$V = 4500$$ 6. **Interpretation:** The volume of water in the tank is 4500 cubic inches. **Final answer:** $$\boxed{4500 \text{ inches}^3}$$