Betta, fry and other small fish will NEVER get stuck up into the filter. These fish, especially Betta, generally dont like vigorous currents, they prefer calm and steady water. This filter is designed to have slow current to easily let betta, goldfish discus, dwarf cichlids, guppies, and krill fish, continue breeding and spawning comfortably. The minor bubbles that are created by this sponge filter creates a nominal current, adding in bubbling water. This will encourage them to continue breeding and spawning comfortably. Also, the sponge filter makes a home for fish food supplementing their daily dose of diet or food intake. It only requires an air pump and airline tubing (sold separately) to work. These create numerous minute bubbles for increased oxygen flow. Simply connect an air pump to the top-center of the filter, then place it in your tank. Please note, the base of this noiseless filter is not weighted, so you may need to weigh it down. It is suitable for tanks up to size 10.5 gallons. Use 2 or more filters in larger tanks. This low-cost sponge filter can be used multiple times. Instead of tap water, use water from the tank to clean it, during a water change. Simply rinse and squeeze a few times, until you see the water run clear from the sponge.