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Hi folks,

I read about a ratio of 60 - 100g of feed per day per square meter of grow bed.

Does this make sense or sound about right to those who have been at this for a while?

I'm going to assume it depends on what you are trying to grow - nitrogen hogs would do best at the high end of the ratio.

I guess this would lead to my next question, how much does a fish eat in terms of body weight?

I'm trying to calculate the number of fish I need for my yet to be built greenhouse system so I know how many fish to get.

Thank you for taking the time to read and respond if you do.





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That is an interesting way to look at it. 

You could also figure how many fish a year you can deal with give them 5 to 10 gallons per pound (fully grown) and decide your fish tank like that.  You may need to tweak your numbers after you figure out how much space that tank will take up. 

Yes, I have heard Dr. Rakocy say those numbers for the UVI system, but if you are using media it is likely to be less because the UVI system removes much of the solids while a system with media does not. In the talk I heard 85% of that feed amount if you don't have solids removal, however in my experience with my system it is even less than that.

Thanks for the feedback,


So Jonathan, removal of the solids having a significant impact makes a lot of sense so 85% would give me a range of 85 - 51g per meter, for media growing. Any thoughts on what a hybrid system would / should run at?


I've been feeding alot less as well all summer, there's not enough fish obviously :) but at the same time the growth on the plants was ok for me. I guess what I'm driving towards to a way to calculate the number of fish I need and the ball park the feed consumption / costs for a given size system. Not an exact science by any means just hoping to have some idea of what the operating cost will be.


Found this feeding table, showing feeding consumption by body weight at different stages of growth:


The table is at the bottom of the page.

I have a system that is 0.37 square meters and I don't use more that 4-7 grams a day to feed the two 5" inch gold fish in there, so I guess i'm feeding in the range of 12-20 grams per square meter and still getting lush growth. My system is a year old so the nutrient profile is pretty good.

If your goal is to grow fish for consumption then you would probably want a UVI type system that would filter out the solids. This way you could feed at the optimum rates for fish growth which requires more feed than keeping the fish for sole purpose of growing plants.

Ok, so just to put a few numbers to things here, I have a greenhouse we picked up used it's 14' x 28' so 392 ft sq, I'm thinking I get half and the wife get's the other half..........assuming we're both still happy with the marriage and want to keep it that way.........a safe assumption. For easy figuring I should be able to create 100ishk sq ft of growbed / raft space in my half along with a couple fish tanks dug intot the ground. I'm thinking hybrid system since I want to grow a mix of things and find the media rather a costly part of the overall system although the rafts are not free either.

Anyhow, back to the calculations, 100 ft sq is about 9.3 sq m so that would be 558 - 930g would be the range of feed per day on this system using Dr. Rakocy's suggested range of 60 - 100g per sq m. Based on a local pond supply place, the least expensive feed seems to go for $5.00 per Kilo, so my feed cost should range from $2.79 - $4.65 per day..................ha still cheaper then having another kid!

Like I said before if you are going to do a Hybrid system and all the solids remain in the system you will probably need something more like 30-50 grams of feed per day per square meter or maybe even less. You will find that you can grow a lot with just a few fish.

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