ok so I want to make a 270 gallon plywood tank, but if I do I probably wont be able to put sand in for a couple months after it's done. Soooo I was wondering if I could put in that much sand after my tank is already running with fish in it? would I just have to lower the water when I do it? thanks for reading, I just would want my fish to be safe especially when I will be getting more expensive ones as I further myself in the hobby.