Review on Premium AQUANEAT Bio Ball Filter Media: Ideal for Freshwater Aquariums, Marine Fish Tanks, Canister Filters, HOB Filters, Refugiums, and Koi Ponds – 1 Gallon (2000g) by Angel Bright

So far I really like these biospheres. They are a little under a quarter as you can see in my photo and very porous. Unlike other reviewers, I got these balls for a full gallon. I contacted the manufacturer prior to purchase regarding the size difference and was told there were several people selling these balls, however if you purchase from the CELLPETSUPPLIES store on Revain you will be given the sizing in gallons. In my picture I have included a gallon size zip lock and a quarter for comparison. I hope they hold on; If I think about it in a year, I'll do an update.