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So I've read it over and over and experienced it myself: small aquaponics systems are unstable.

Below a certain size (200 gallons?) things change fast and your system can crash in a single weekend.

The question is why?

If I have a 200 gallon setup with (20) 2 lb fish, why wouldn't it be just as stable as a 20 gallon system with (20) 2 oz fish?  

I know it's not, but why not? 

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I have a 27 gallon system (approx 8oz of fish) that I haven't touched in 2 years, I just use egg shells to buffer which have lasted more than a year. My keys to stability are having a small fish population, feed a small amount once a day or less and at least a 1:1 tank to grow bed ratio.

I have 2- 45 gallon tanks that I can't keep the PH up on and the ammonia/ammonium stays high even with water changes. One tank has 7 6-8" goldfish and one has 14 3-4" Tilapia. I also have a 300 gallons with 800 3-4" Tilapia and 10 adults Tilapia. The only problem with the IBC is 7.3-7.4 PH and I don't worry about that. I guess I'm just confirming what you've stated Jeremiah. Don't know why for sure but the larger tank seems to be self buffering. I'm going to add some calcium carbonate the 45 gal. tanks to try to create a buffer and raise the PH. Then I'll probably worry about the ammonia.

So you both have really low stocking rates.  I'm wondering why a higher stocking rate (my 450 gallon system can hold 100 x 2 lb tilapia)?

From what I've read your ratio is about right. I know that this summer I am going to have to make changes to my 300 gallon tank since the 800+ Tilapia are starting to really grow. I can bump what I have up to 500-600 gallons without adding a tank but it still won't be enough. Know anyone that needs some 3" fingerlings?

Back to topic, I just re-watched this series of videos last night and a light bulb went off in my head as how to control changes in my smaller tanks. https://www.youtube.com/watch?v=jb5oSzLXTwU  . It really covers more than just raising and lowering PH.

Larger systems have larger room for error, things swing more slowly giving you more time to act. That is really the only difference. With my small system I found just found the right balance of parameters to keep it stable.

Jeremiah, are you running a DWC or media system?

@Jeff: I hope to watch your video soon.  Pretty busy at the moment.

@Jonathan: The question is why?  Why are larger systems more stable.  I have a media system, and a separate DWC system I've been building.

@Jeremiah, @Jonathan, The video I mentioned talks about buffers. This is why bigger systems are able to react slower than smaller ones I think. In my earlier days I was so busy looking for information I missed a lot of what I was seeing. This video is a perfect example of that. I was looking at how to adjust PH and missed the real message about buffers.

@ Jeremiah Maybe I am stating the obvious, but my point is a 400 gallon system would respond 20 times slower to a mistake or a problem than with a 20 gallon system. A small issue like over feeding by 20% is much more likely when you are feeding 2 fish as opposed to 40 fish. Errors that might not be noticed in the smaller system would be obvious in a larger system. It is kind of like comparing the navigation of a supertanker vs a yacht. one is going to be much more sensitive to the commands of the captain.

Maybe I'm wrong, but from everything I have learned to this point says everything that matters in an AP system takes place either at the microscopic or molecular level. If that is true, than really size doesn't matter other than the users ability to control the inputs and environment at whatever size.

Am I making sense?

Good explanation Jonathan. And it's easier to overfeed a small system than a larger one.

I think I hear what you're saying.

Basically if I did everything with measuring spoons and droppers the systems should be just as stable no matter the size.  Is that right, do you think?

That's about it.

I do use droppers all the time measuring in milliliters for a 17 gallon system. The equation of 20 drops per ML is something that factors in to how I control my systems.

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