I'm getting confused by the calculation required to see if I have enough bed space. I have a 6' round kiddie pool 18" deep it can hold around ~300 gallons but I'm keeping it about 3/4 full so around 250 gallons. Currently I have about 2 dozen goldfish in there. This is just my trial system to see what and how it works.

I'm using 3' x 2' x 8" deep concrete mixing tubs as grow beds. Currently I have 2 but want to expand further and it is in the plans for more beds. I'm thinking I'm under the suggested amound of grow space.