? about Balancing Fish and Plant Ratios:
(From student after the March Abundance Foundation workshop)
1. For my outdoor system (even my indoor system) I STILL can’t figure out the ratio thing…meaning HOW do you know you can grow 3 heads of lettuce to 1 lb fish and 1 tomato plant to 6 fish.
What I am trying to figure out is that I want to grow peppers, lettuce, tomatoes, snap peas, broccoli (for example) and I have two grow beds 4ft X 4ft (16 square ft ) and 12inches deep (16 cubic feet= 119 gallons)…attached to a 200 gallon tank. Help?
Dear M, remember to use the rule of 1lb fish/sq ft of planting area (derived from Rakocy's feeding ratio of 60-100 g feed/m2/day)
1st determine # of fish needed to maintain the desired plant bed size.
1lb fish/square ft : if 16 square ft then 16 lbs of fish required
Fish density?: 16lbs of fish/200 gallon tank = a density of 1lb fish/ 12.5 gallons
Notice your plant bed:fish tank volume ratio is ~1:2 (119:200) which will work well with media beds and in fact this is a great fish density to start with since it will be easy to maintain at this low density
2nd determine # of plants based on max planting density:
if 16 square ft= then ~45 heads of lettuce can be planted (max. planting density= 2.8 heads/sq ft)
or 3 tomato plants (planting density- 1 tomato/6 sq ft)
[note 45 heads/16lb fish = 3 heads/fish & 3 tomato plants/16 lb fish= 1 tomato plant/ 6 fish]
You can do any combination of lettuce or tomato plants in the 16 square ft, just make sure you plant them at their max density.
Question 2. I am still unsure how to figure out how I can grow 6 heads of lettuce, 1 tomato plant, 2 bean plants and 4 heads of broccoli… Because I don’t know how to figure out how many fish I need for bean plants and how many fish I need for broccoli…does that make sense? Even Strawberries, how many fish do I need for strawberries…
It is true that there are more mathmatical models to tell you exactly the number of fish to plant ratios required for a given plant species but unless you consult with someone like Dr Wilson Lennard who would have these exact numbers, you have to just use the 1lb fish /sq ft as a rule and plant at the max plant density- let your eyes guide you to whether your system is balanced- nutrient deficiences can be detected (e.g. plant coloration strange may mean nutrients are limiting because either more fish are needed, feeding rate is too low, or pH not optimal etc) and chemical tests can be used to detect imbalances (e.g Nitrates too high- more plants can be added to absorb all the nitrates etc).
Please PLEASE let me know when your quick reference handbook is available to purchase!!
I am working on it and should be available soon!