Keeping Moss Balls Round

Offer strong lighting. Proper lighting is required for the moss ball to photosynthesize energy. An aquarium with moss balls should be lit with about 3 watts of fluorescent lighting per gallon. For example, a 10-gallon aquarium should be lit with bulbs totaling at least 30 watts.

Introduce a liquid aquarium plant fertilizer, which contains nutrients like phosphates and carbon dioxide into the water. The moss balls use these nutrients and the extra carbon dioxide to promote growth. As long as they're growing and healthy, they won't start to go flat.

Clean the moss balls regularly. The balls pick up a lot of dirt and debris as they roll around the bottom of an aquarium, and this debris weighs them down. They may start to flatten out if they get weighed down. Take the balls out every week, and rinse them under warm tap water to remove as much debris as possible.

Use powerheads in your aquarium to create a current. Powerheads suck up water, then spit it out in a jet stream. The more the balls move around, the longer they retain their spherical shape.