Wolf3101 I hate to disagree with you... I wouldn't put a 103 on the 30 and say that it will handle it no problem... these filters were actually in use up to 30 years ago according to my research... they are only rated for 103 gallons per hour when it was new... at best now it's prob only pushing 70-80? A 30 Gallon would need a min of 120 gallons per hour...so he's better off using this on a 10 -20 IMO