Hi, how do you keep the fish from going in the pump inlet? Are the scrubbies or bio balls just in a pipe with the water flowing around them on it's way to the plants? I have a hydroponics setup with 21 dutch buckets with tomatoes and cucumbers and an NFT system with Brussels sprouts, spinach, string beans,cabbage, and broccoli and I would like to add a fish tank with tilapia in it. Do I need a place in the tank with gravel for the fish to lay eggs in? Jay