| I can't really answer your question about the bio balls but 2000 gallons is not enough water for 12 koi.
As SteveC says, it's a system. You can't isolate just the 3000 bio balls as your filtration and say it's enough.
I just bought 4000 1" bio balls to use in a shower but I have 12 cu ft of additional media in moving beds. |