I can't remember the flow rates either right now but I do know that the UV light I bought for my 72 gallon tank is oversized and would work fine on a 100 gal tank. I got the 18 watt UV sterilizer from Lowe's. It's $99 and works as good as any specialty aquarium light. It is marketed for ponds... The only drawback is that it is pretty large. Most aquarium lights are helix designs which allow for a more compact package but they cost a lot more. The one from Lowe's is just as good and also has a quartz sleeve that the better units have. The only thing that some UV lights have that this one doesn't have is a wiper. This is an internal blade that wipes any haze off the quartz to keep it clean so that all of the light can pass through. Overall I would recommend it.