Aquaponic Gardening

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So how many fish can I have in my 300 gallon tank? or how much Raft do I need to support 60 lb of fish? This is the place to share the numbers for designing a well balanced system.

I know the numbers for Flood and drain media so that is what I will share and I'll let the experts on rafts share that info.

Standard rule for media systems is (Actually this is MAX and only for the skilled fish keeper.)
3 kg of fish per 100 liters of flood and drain media (those fish can be living in 50-100 liters of water, and a sump tank could be necessary to provide extra water if the fish tank is on the small side of the numbers) So to convert that to measure that we think in more commonly.
5 lb of fish per 25 gallons of flood and drain media.

A more appropriate recommendation for fish stocking would be 20-25 fish (500 gram grow out) per 500 liters of grow bed or 1 fish per cubic foot of grow bed with a planned grow out of 1 lb.  Total grow bed and fish tank should be of equal volume or if a sump tank or indexing valve is used there can be more grow beds than fish tank up to twice as much grow bed as fish tank.

Perhaps this might be a little conservative but it is better to start light on fish while cycling up a new system. Once you get comfortable you can decided how best to keep the fish.
A big note here. Those fish weights are for the planned final grown out weight of fish in a system.

Example, say you have a 300 gallon tank and 300 gallons of flood and drain media filled grow bed.
Say it's a simple system pumping from the fish tank to the grow beds which drain back to the fish tank. Say you are growing tilapia and you plan to grow them out to 1 lb if you can.
I would say stock only about 60 fish. (I'm not into planning on lots of fish deaths so I would only personally pad this number by a few fish-I would not personally stock 100 fish and plan on loosing 40.) Again this is assuming that you will grow all those fish out to eating size in that same tank. Again these numbers are a bit skewed, Kinda figuring people would start eating their tilapia a bit smaller than a pound to make enough room for the other fish to get to a pound.  Also, tilapia tend to allow people to pull off higher numbers than are really possible with most other types of fish.  In such a 300 gallon 1:1 system I am currently growing only 30 catfish.

They start small in a new system and give you time for the bio-filter to cycle up to the load.

Some other handy numbers for figuring out pump sizing and aeration.
You want your water pump to cycle the equivalent of the volume of you fish tank each hour at the amount of head you are requiring of it. So for that 300 gallon system, if you run the pump continuously and use auto siphons to drain the grow bed, you need a pump that will do about 400 or 500 gallons an hour. If you wish to use a timer and flood all the beds together 15 minutes per hour, you need a pump that will move that 400-500 gallon in15 minutes so you need a pump that can do 1600-2000 gallons per hour. Another option is an aquaponic indexing valve where you could pump for a period of time to each bed in sequence. Figuring out the pump required for this will depend on the indexing valve chosen and the timer one wishes to use.

On pumps, do some extra research, a cheap pump often uses more electricity so it may cost more in the long run than the costly pump. Always look for performance curves to tell how much flow can be expected at different head heights. Remember that small plumbing will reduce efficiency, never restrict your pump output.

On to air pumps. This will definitely be different than the DWC system since for a media system, you only need to aerate fish tanks/sump tanks. Aeration of tanks helps keep solids moving along and not collecting in with the fish. Aeration will also assist the fish in being able to metabolize food and grow faster. If there is not enough oxygen, fish don't eat as well. Highly aerated water also assists the bacteria where ever they may form to convert ammonia and nitrite to nitrate. It also assists in keeping the water circulated to avoid dead spots and brings bottom water up to the surface for better aeration in that way (it isn't just the bubbles contact with water that aerates.)

Aeration numbers. Simple rules of thumb I've been told.
You want 1 cubic foot per minute of air for each 400 gallons of fish tank. You need 1 psi to push air though the air stone and 1 psi to push air down 28 inches under water. So for the average system you want to figure out how much air an air pump will provide at 2 psi and then figure out how many cubic feet per minute you need to provide for your system volume.
I have a 60 watt air pump that provides 2 CFM at 2 psi. That air pump runs all the time. Normally it runs on mains power but I have installed a relay so that if mains power goes out, I have a deep cycle battery that will keep the air running to my system for at least a day. (So there is aeration and backup all in one air pump plus the appropriate batter, charger, inverter and a DTDP relay.)

Air I'm sure is a completely different story in Raft culture and I've heard of raft systems being run almost completely on air with minimal water pumping. But I know almost nothing about blowers so I'll leave that explanation to others.

Some notes about plumbing. Gravity drains always need far larger plumbing than their pumped counterparts. For example. If you are pumping into a tank using 1" plumbing, you had better make sure your gravity drains and overflows out of that tank are far larger than the 1" inlet or the tank will overflow. Don't make your overflows too close to the rim of the tank or they might not have a chance to work before the tank actually overflows over the top. You need enough fall or height for many gravity drains to work, it might not have to be a lot but you can't drain uphill by gravity. So if you are gravity draining from a fish tank, make sure the place to which the water drains to is lower than the high water level in the fish tank or it won't work.

If in doubt about plumbing, go bigger. It is easy to reduce down later if you need to but if the hole or bulkhead is too small, it can be difficult to up-size later.

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I see two different goals people are aiming at here (and I essentially agree with all of them) but we might want to sub-divide a bit here.

One of the goals that I think Sylvia and others are after is a very simple basic Rule of thumb Starting point so to speak for Hobby based or learning systems.

And I see others are hoping to dig more in detail and quantify more of the lesser known variables (like how much and in what way do worms affect a given systems ability to support fish.) Or get into exact ratios for combination systems. I think this is great when expanding the field but please share the details because the devil is in the details when it comes to things like this.

Now while both these goals are great, I do think it is important to make sure the new comer does not miss-apply the numbers they find. So for Sylvia's bullet link of Rules of thumb, please keep the numbers to the recommended low density stocking levels. I've run into a few people who were trying to stock a system by UVI's numbers but they had neglected to apply any of UVI's extra solids removal, bio-filtration, or supplemental aeration. Basically they were trying to stock a friendlies Low Density trimmed down system with UVI stocking rates which don't really mix and match well.
Well I've not run a system completely fishless super long term yet so I can't say exactly how long it would last. And there are tricks that I know would make it last longer like the trick of feeding veggie scraps to the worms in a corner of a grow bed. It would also depend on the type of plants and how heavily they feed as well as how much one harvests and removes from the system. The Aquarium system inside the house has been fishless for not quite a year yet I think. The nitrates are still high but it is only growing house plants. It does get little doses of the extra sample water I bring in from outside (what doesn't get used in the test tubes I usually pour into the aquarium from the sample cup) so it is getting perhaps two-six cups of water from the outdoor systems each month. Those house plants do suck a fair bit of water out of that system and I probably add a couple gallons of tap water each month.


Kate Mink said:
With no expertise whatsoever I'm guessing that established gravel beds develop a biotic community something like soil, and that's how TCLynx can run low fish or fishless for considerable periods. The interesting question is whether this is self-sustaining or runs out eventually.

Kobus, I totally think the discussion on the more advanced scale should totally keep going and this forum is for all levels. And I think this thread is even a fine place for it.

I just think the Rule of Thumb or the "starter numbers" (That Sylvia is planning to put as a quick bullet point link on the main page) when handed out are the ones meant for the newbies who are learning.

It is often hard to keep people from trying to run first I will still recommend that we default the treadmill to a crawling or walking pace at initial start up and it is easy enough to dial up the pace from there.
Many people simply can't grasp and use principles in the absence of examples and specific "how to". Others have just as much trouble with "do this" in the absence of the theoretical explanation. (There's theoretical literature on this, but what I say is more based on my experience as a high school teacher and adult educator.) Just as with systems, there's no one approach to learning. Some people start by copying something that's known to work, others read up on the subject, still others have to start with some new idea of their own, because that's what motivates them (yes, it often fails. That's also how we learn. Someone told me once that you're not an aquaculturist until you've killed a million fish. Ouch.)

I like the idea of a site with info for all, but where it's easy to see whether a page, thread or post is at the intro, intermediate, or advanced level (like the trail markers at ski slopes.)


I do not think it is a good idea to "stick to low density" when advising people on numbers. Trying to run a Friendly like a UVI is like filling a diesel car with jet fuel, and is EXACTLY why I say people should be made to understand the underlying principles of each system. Whoever did that did not understand the first paragraph of biological filtration or system oxygen demand. If they did that by themselves then shame on them, but if they did that after getting help, they were not fed the first principles first up.
Kate Mink said:
I like the idea of a site with info for all, but where it's easy to see whether a page, thread or post is at the intro, intermediate, or advanced level (like the trail markers at ski slopes.)


Oh, I like that idea Kate
brilliant, if feasible, covers exactly what I'd mentioned in the "improvements to site" thread!!


TCLynx said:
Kate Mink said:
I like the idea of a site with info for all, but where it's easy to see whether a page, thread or post is at the intro, intermediate, or advanced level (like the trail markers at ski slopes.)


Oh, I like that idea Kate
I'll try to get a Simple Rules of Thumb for Media Based Home systems up on the home page by the end of the week, along with some verbiage at the beginning about that this is for beginners, and encouraging the reader to delve into the rest of the discussions to learn the whys behind the rules, the variations to the rules, and the deeper ideas that are contained therein. I'll also send them to Friendly's website for their system, Travis's website for Barrellponics, and the UVI website for their info. I'll leave the comments section up for a week or so so members can comment. Sound like a reasonable plan?
I'm sure both Joel and Murray will no doubt comment shortly...

But Dr Wilson Lennard has just released an "backyard aquaponics system sizing tool"....

You can download both the modeling spread sheet, as well as the "how to" explanatory notes, right now.

The metric calculator (excel) :
http://www.backyardaquaponics.com/Travis/Aquaponic%20media%20bed%20...

The imperial Calculator (U.S.) (excel) :
http://www.backyardaquaponics.com/Travis/Aquaponic%20media%20bed%20...

The How to notes (pdf):
http://www.backyardaquaponics.com/Travis/Aquaponic%20media%20bed%20...

You can visit Wilson Lennards website here http://www.aquaponic.com.au/backyard.htm

You'll also find the links on Murray's forum site as well.....

So what are you waiting for, download the modeling calculator and see how your systems stacks up to the scientific recommendations.



Sylvia Bernstein said:
I'll try to get a Simple Rules of Thumb for Media Based Home systems up on the home page by the end of the week, along with some verbiage at the beginning about that this is for beginners, and encouraging the reader to delve into the rest of the discussions to learn the whys behind the rules, the variations to the rules, and the deeper ideas that are contained therein. I'll also send them to Friendly's website for their system, Travis's website for Barrellponics, and the UVI website for their info. I'll leave the comments section up for a week or so so members can comment. Sound like a reasonable plan?
It also represents the "thought processes" that originally went into the suggested stocking densities and tank/growbed ratios... which just weren't properly explained or expounded upon...

Kobus Jooste said:
I like this one already. It is 100% media-based though, so I will have to tinker with it, but at least it is based on the filter configuration, fish stocking rates and feeding data (volume AND food protein content). The output is also very good in my view as it gives you the other critical stuff such as flow rate and surface area of the filter. With the surface area I can mess with raft stats to get an idea of the overall characteristics of my system in terms of root surface area, which is a much more intuitive approach as compared to a rigid tank to gravel bed ratio that does not consider all the other critical variables. This feels a lot more like the thought process I went through originally designing it.

RupertofOZ said:
I'm sure both Joel and Murray will no doubt comment shortly...

But Dr Wilson Lennard has just released an "backyard aquaponics system sizing tool"....

You can download both the modeling spread sheet, as well as the "how to" explanatory notes, right now.

The metric calculator (excel) :
http://www.backyardaquaponics.com/Travis/Aquaponic%20media%20bed%20...

The imperial Calculator (U.S.) (excel) :
http://www.backyardaquaponics.com/Travis/Aquaponic%20media%20bed%20...

The How to notes (pdf):
http://www.backyardaquaponics.com/Travis/Aquaponic%20media%20bed%20...

You can visit Wilson Lennards website here http://www.aquaponic.com.au/backyard.htm

You'll also find the links on Murray's forum site as well.....

So what are you waiting for, download the modeling calculator and see how your systems stacks up to the scientific recommendations.



Sylvia Bernstein said:
I'll try to get a Simple Rules of Thumb for Media Based Home systems up on the home page by the end of the week, along with some verbiage at the beginning about that this is for beginners, and encouraging the reader to delve into the rest of the discussions to learn the whys behind the rules, the variations to the rules, and the deeper ideas that are contained therein. I'll also send them to Friendly's website for their system, Travis's website for Barrellponics, and the UVI website for their info. I'll leave the comments section up for a week or so so members can comment. Sound like a reasonable plan?
Hum, went and had a play with that tool. And read the pdf.

I don't know, according to them, It seems my system should have had all it's media washed or vacuumed about 10-12 times by now to keep things working properly and that my grow bed surface area is still 4 times too small.

To go on about how deeper beds would be better for bio-filter and solids mineralization but then insist that even if they are deeper that they still need to have the same amount of square footage since only the top few inches actually work very well for aerobic solids mineralization seems a bit contradictory.

And then they are only suggesting a flow rate of about 1/5th of the fish tank volume they suggest.

Perhaps the design of my system isn't very scientific but it is working fairly well so this doesn't lead me to endorse this tool very highly. On a scale of 1-5 at the moment I would probably only give it one star.

Now if it could handle showing different needs based on different flow rates, perhaps it would give a more accurate picture
I just finished reading it as well. While I am an absolute fan of Dr. Leonnard, and I absolutely appreciate that he has made available for free what obviously took a tremendous amount of work, I'm hoping that this tool is just "round one". I found that his attempt to create an all-encompassing tool that would work for both DWC (UVI) and media based systems confusing, and unfortunately, the Imperial worksheet was actually a combination Imperial and Metric, further adding to my brain pain. As you guys know, my focus is often on how can we make aquaponics approachable for the average person, and I'm afraid this isn't going to help...at least not in it's current form. But, again, much thanks to Dr. Lennard for the work that went into this. I look forward to seeing it evolve.
Kobus, were you using the Imperial spreadsheet? That is the more confusing one as it has the data entry in Imperial, but all the explanations are still in metric....


Kobus Jooste said:
O dear - I see two design philosophies developing. Those that treat AP as having to adhere to the first steps of aquaculture philosophy before it hit the plants, and those that get headaches from that way of arguing! I look at that spreadsheet and it all clicks into place for me.......

As I said earlier, it seems to work according to how I have always pictured these set-ups of mine as having to work. Everyone to his own understanding then! Luckily there are so many ways to build these things!

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