The Marina Flexible Coil Brush is ideal for cleaning filter tubes. This can reach up to 1.9 cm (3/4 in) in diameter and 53 cm (21 in) in length. Your fish depend on you having clean filtered water. To help accomplish this you must maintain your equipment every few weeks. Keep them healthy and thriving by cleaning your tank often. These brushes don’t have to be purchased often if you keep them in good condition.