Microbubbles are truly tiny, tiny bubbles, pinhead-size and smaller -- microscopic. Many types of aquarium equipment can generate microbubbles but, paradoxically, they can interfere with many other types of aquarium equipment. You can prevent or mitigate microbubbles a handful of ways.
Many types of aquarium equipment can generate microbubbles, including water pumps, spray bars and power heads. In fact, some aquarium equipment intentionally creates them. For example, without microbubbles, protein skimmers could not purify aquarium water. Unfortunately, microbubbles tend to collect in aquarium plumbing, merging to form bigger and bigger bubbles that block the plumbing, causing floods and other aquarium disasters.
You can build special screens to prevent microbubbles. Screens usually consist of filter floss or sponges. Positioning them in front of inlets and plumbing vulnerable to forming bubbles can reduce microbubbles. As a bonus, these screens can help collect debris. This is also the downside to screens: If they collect enough debris, screens can clog, blocking the plumbing and causing the problem they were meant to prevent. If you use this method, you need to check your screens daily to weekly, depending on how much debris is present in your aquarium.
Baffles are just little mazes that microbubbles have to navigate as they propel upward. Baffles guide bubbles away from sensitive equipment and plumbing. Unlike screens, they cannot be blocked by debris. However, baffles require implementation from the very start of setting up your aquarium. It is next to impossible to install baffles on a running aquarium. Additionally, they may require wide sumps to accommodate them.
A float switch does not prevent microbubbles but can prevent the serious flooding they cause. A float switch consists of a float attached to two contacts. You can wire a float switch so that the sump's return pump shuts off if the main aquarium's water level rises too high. This way, if microbubbles break your siphon, the return pump shuts off instead of continuing to pump.