The drain from your aquarium can create excessive bubbles in your sump or refugium. Some of these bubbles may get removed by the bubble trap, but chances are some are making it back into your display. To help alleviate these bubbles, some hobbyists run their drains into bubble towers. These towers are usually tall towers filled with live rock or some other media, and do a great job of isolating excess bubbles before they get dispersed in your sump. If your sump is already installed under your aquarium and the drain is creating tons of bubbles, installing a bubble tower may not be possible. Instead, you can stack up rocks or use some filter material to trap the bubbles.