Sounds like things are GOOD for you Sunnie. Here's what sizes they are..
Reef Balls
Large apprx 5" tall, 8"base diameter 6lbs
Med apprx 3.75" tall, 5"base diameter 2lbs
Small apprx 2" tall, 2 1/2"base diameter 1lbs
Reef Cakes (One AVERAGE size only)
8" to 10" tall, 9" at base, weight about 10 lbs
Small would work great in a smaller tank. I plan on putting a Small and a Medium in my 10g tank.
