Basic Aquaponics System Design- The Things I so often repeat

[TCLynx]

Now we are probably getting into some of the stuff Sylvia really wanted me to write about. In some places I'm known for my patience in re-explaining many of the basic info needed for stable home aquaponics system design.

Things like the three major functions of media filled flood and drain grow beds (actually there are more than three functions.)
1-Media filled flood and drain grow beds provide Bio-filtration
2-Media filled flood and drain grow beds provide solids filtration
3-Media filled flood and drain grow beds provide plant support and space for growing
Now we get into the additional functions that many people might forget about.
A-Flood and drain media filled grow beds do all of the above functions without needed any additional aeration added to the system
B-Flood and drain media filled grow beds provide a great home for composting worms.
C-Flood and drain media filled grow beds provide for mineralization of solids.
D-Flood and drain media filled grow beds don't require net pots or separate seed starting facilities.
E-Leaves don't foul up outdoor flood and drain media beds
F-Algae isn't a problem in flood and drain media beds
G-Flood and drain media filled grow beds give you a place to set down your drink as you use extravagant hand gestures to explain some point during an Aquaponic gathering or system tour.

Perhaps there are other points in favor of flood and drain media filled grow beds but there are a few points on the negative side.
-Flood and drain media beds can have a huge impact on temperatures, they make very good chillers on cold nights and they are great water heaters on hot summer afternoons. (constant flood during these times might be appropriate.)
-Gravel is heavy and a pain in the back to wash/haul.
-Lighter manufactured materials are costly and still need rinsing.
-Flood and drain causes water level fluctuation or requires a sump tank or sequencing valves.
-timed pumping can be hard on pumps
-variation in sounds from pumps turning on/off or siphons kicking in/out draw attention to the noise (constant sound fades to the background most of the time.)

Still, I like the gravel beds for their ease of use once installed. If a system is properly designed (has enough grow bed to handle the fish load) the gravel beds provide for a very low maintenance system able to be left to fend for it's own for a few days. This is important as I travel often and need something easy for the neighbor to check on. If you are going to do NFT or Raft(DWC) systems, you will need separate ways to deal with solids filtration and bio-filtration. With media beds, they take care of solids, bio, and plant space all in one.


Next primary bit of information people often need for designing their home system. How much filtration is needed for some given amount of fish. Here is the rule of thumb I learned.
3 kg of fish in 50 liters of water with 100 liters of grow bed or 6 kg of fish per 100 liters of fish tank with 200 liters of grow bed. THAT IS THE MAX!!!!! Ok so for my poor brain I rounded that out to an easy imperial measure to remember. 1 lb of fish per 5 gallons of gravel (again that is MAX!) Now keeping in mind that you can't really flood 100 liters of grow bed from a 50 liter fish tank and expect your 3 kg of fish to still be happy. To run this 2:1 ratio, you must have some method of dealing with water level fluctuations. That method traditionally was a sump tank, now there are more options with things like indexing valves.

Instead of using the above numbers, I now usually recommend something more like 20-25 fish per 500 liters of grow bed (assuming fish only being grown out to 500 grams) or 1 fish per cubic foot of grow bed media assuming 1 lb grow out of fish (1 cubic foot is around 7.5 gallons.)

Now I would never recommend some one try to grow a 1 lb fish in only 2.5 or even 5 gallons of fish tank. I've read a few places that say you can grow an eating size fish in something as small as 50 gallons, well perhaps you can with a fish as forgiving as tilapia but I like larger tanks. Very small fingerlings are fine in small tanks and I currently have over 100 small catfish in a 100 gallon tank but for grow out of large fish like catfish, my personal minimum size tank would be 300 gallons. I like a 600 gallon tank to grow out really big catfish. 300 gallons is also a good size to have more temperature stability.

Pumping now this is more important that many people think. How big a pump do I need for my system? Well the simple rule here is you should aim to pump the volume of your fish tank each hour. So if you have a 300 gallon fish tank and your design will have the pump run constantly, then you need your pump to move 300 gallons per hour at whatever height you will be asking of it. (A pump with a nominal rating of 300 will probably not move 300 gallons per hour once you hook it to plumbing and expect it to lift that water two feet above the surface of the fish tank.) Most good pumps should have published curves or information that will tell you aprox how much water it will move at different head heights. Now if you are going to be doing timed pumping, you need your pump to move at least the volume of your fish tank during whatever portion of an hour you will have your pump on. So if you plan to run 15 minutes each hour, then you should get a pump that will move 4 times the volume of your fish tank at the needed head height each hour. Then when you run it for 15 minutes, you will get the circulation you need. It is always wise to allow extra flow a bit beyond what you think you will need.

Plumbing and pipe sizes. Oooooh this is a stinger
So many people start their first systems with too small of pipe and find out later they should have used larger. Yea, the bigger pipe and fittings costs more but buying both the smaller stuff and a set of the larger stuff costs even more yet. Please remember that in Aquaponics there is this stuff we call bio-slime that can clog small piping. Algae can clog piping as well. For larger pumps, I'll connect the pump according to the pipe fittings the pump comes it. for small pumps, I now adapt up to larger pipe and I've found that a little tiny pump can sometimes actually move much more water than I expected. Even my ten gallon aquarium with a 20 watt pump is adapted up to 1" and 3/4" pipe.

Gravity drain plumbing, MAKE IT BIG!!!
Example, My big system, the pump uses 1 1/2" pipe, about half of the flow from the pump is being sent to the fish tank (probably 30 gallons a minute) the SLO (solids lifting overflow) drain from the fish tank is 3" sewer pipe. If I were to send all 60 gallons per minute from my pump to the fish tank, it would overflow even with the 3" drain. I know it is a real bummer cause the really large fittings get costly but so would overflowing the system and burning up the pump when the sump runs dry. Some people will use two 2" fittings instead which can work but keep in mind that the more pipe walls you are dealing with the more resistance. In other words, two 2" pipes does not equal one 4" pipe. A pump pushing water through a 1/2" pipe can still over top a 1" overflow. And then remember that the overflow will probably have grills or mesh over it and that can clog too (on to a next important point.)

Fish will swim through pipe.
I've had a 2 inch fish swim through 3/4" piping with six elbows! I've had tilapia fry make it through a gravel bed to get into the sump tank where they rode through the pump to get into a different fish tank!!!! And one of them survived!! But you can't expect them all to survive or even expect any of them to survive. Most fish find that sunning them selves on the surface of a grow bed to be very bad for their health. However, finding the fish on the grow bed is a little more pleasant than discovering one in a ball valve, or more accurately part of one in the ball valve "I wondered why that was so hard to close!" I've found that most fish find NOT swimming after eating to be very dangerous. I guess this will bring us to the next topic, tank covers. Most of the fish I find out of the tank get eaten by something else, like my chickens.

Fish tanks should have covers.
1-Fish tank covers keep fish in. Any fish tank that doesn't have a huge amount of extra depth above the water line risks fish jumping out.
2-Fish tank covers keep debris out. In outdoor systems things like leaves can really clog up the works. Even with a tank cover some leaves are gonna get in but a cover will keep huge amounts of plant matter out of your fish tank and also the screens, grates, pumps, traps and plumbing.
3-Light. Shade the tank to keep excess sunlight out and avoid a major algae bloom. Pea soup can really mess with dissolved oxygen levels even to the point of killing fish. String algae can just gunk things up and create more work in pump/screen cleaning. A cover over the tank will keep light out or at least make it easy to throw extra fabric, shade cloth or a tarp over to block the light and stop the algae.
4-children and pets. Kids love to play in water but if you have children around, make sure your tank cover will keep them out unless supervised. I also recommend covers if you have ducks around or dogs/cats that might manage to get into trouble while trying to sneak a snack.
6-Since my property isn't fenced, I've also added a lock to the cover on my large tank. Yea I know it will only keep honest people honest.

Next topic,
Galvanized tanks, Don't do it!!!!!!
Metals!!!!!!!!!! They are generally not appropriate for aquaponics.
Many metals can quickly corrode in aquaponics. They can build up to toxic levels for fish in a recirculating system. Of particular importance to note are copper and zinc. Both can be particularly detrimental to some types of marine life. Galvanized tanks can leach zinc into water and it becomes more problematic the lower the pH. Copper plumbing can leach too. In our household plumbing this in not normally a problem as the water is only taking the single trip through the plumbing but in an aquaponics system the water circulates through the parts constantly and aquaponics also sometimes tends to the acidic side which can speed the process. Hence a copper coil would not be a good idea for a water heater for aquaponics. There are other metals that can be an issue (perhaps nickle from chipped bathtubs) but copper and zinc are the two that cause the most issues in Aquaponics in my reading.

Media
Look for something that won't affect your pH. This rules out limestone and marble since they will cause a really high pH. Also, I don't recommend shells, my system is full of them and my pH stays at 7.6 unless I'm really overloading it. I've heard that Diatomite will lower pH but one might want to be careful if growing trout in such a system since it apparently also has levels of zinc that might be bad for trout at the lower pH. I like river rock of 1/2" size. Lava rock can also be good if you can get it in the right size range but it is really difficult to get washed very clean. Clay balls are great if you can afford them and your back can't afford the lifting of gravel. I recommend using small buckets and baskets for the washing. I can do the washing so long as I don't lift too much at any one time. Set up the washing station so you don't have to bend over too much and it can be done without injury.

Plumbing a bypass
Don't restrict your pump. If your pump gives more flow than you can handle, then use a bypass. Simply a T back into the same tank where the pump is located. Put the ball valve on that flow and adjust the ball valve till the flows are balanced as needed.

I think I'm about out of steam on this post. All these things I've repeated many times on forums to help out people struggling in one way or another with their physical system designs. I hope these things help more people on their journey into Aquaponics.

[TCLynx]

Jim, when you talk about 1 1/2" or 2" S&D (sewer and drain) pipe, do you actually mean DWV (Drain Waste Vent) pipe?

I can buy 3" and 4" S&D pipe around here but the pipe and fitting sizes are definitely different than the schedule 40 or DWV.  Schedule 40 and DWV pipe and fittings are sort of interchangeable though the DWV pipe has a shallower seat so you need to be better about cutting your pipes straight and depending on where you put them should maybe glue them more often.  The main difference between the "regular" PVC fittings and pipes and the DWV stuff is the pressure ratings.  In a home you would not use DWV pipe for the pressurized lines from the pressure tank or city water supply since it is not rated for pressure.  In aquaponics we rarely have much pressure going on so my comment is sort of academic or to help people understand different pipe sizes.

There are different pipe wall thicknesses and where things get really confusing is that here in the USA our pipe sizes are "nominal" that means in name only.  (Have had a few people get confused lately thinking that the pipe sizes refer to the OD or outside diameter of the pipe which here in the US, they do not.)  Our "nominal" pipe sizes are actually based on ID (or inside diameter) but those sizes were set in the past when the materials and their strengths were different.  Back then they came up with standard size fittings for the different sizes of pipes and those fittings are based more on the exterior size of the pipe, which was based on how big the pipe needed to be to carry a given flow at a given pressure without worry of bursting.  Over the years our materials have become higher tech and they don't need to be as thick anymore in order to be strong enough, However, instead of changing the exterior, which would require ALL fittings be changed, they have left the exterior size alone for the most part and just made the pipes thinner where materials allowed.  This saves on materials and weight while allowing the use of the same old standard fittings.  BUT it is confusing since now days it means that neither the OD or ID have much if anything to do with the NAME we call the pipe size!!!!!!!!

There are other parts of the world where the pipe sizes are named based on the OD and the OD is the exact size.  That is NOT the case in the USA or any place that is using the same size pipes as here in the USA.  I do believe that OZ uses the same size pipes as the USA but if you are in Europe, the middle east, or elsewhere, do some careful research before you buy plumbing parts from the USA to make sure you will be able to make them work.  Pipe sizes are NOT the same the world over!!!!

I have also discovered that even people here in the USA who I would think already know better, don't understand our crazy pipe sizing.  I sent my uncle out to cut a bunch of 1 1/2" PVC pipe for a project and he came back all frustrated because he couldn't find any 1 1/2" pvc in my pile of supplies for the project, all he could find was what he would call 2" pipe.  (He was measuring the pipe, not looking at the labels on it.)  the OD of our 1 1/2" pvc pipe is actually far closer to 2" than it is to 1 1/2".

Also, when you send some one else to the hardware store, it is best to send them with a piece of pipe or fitting in hand to check the size since I once sent some one for 3/4" pvc pieces and they came back with 3/4" cpvc which is a totally different size.

3" or 4" S&D pipe and fittings is going to be very different than 3" or 4" DWV pipe and fittings (though there are some tricks I learned where a nice smooth coupler from the S&D pipe has the same OD as the pipe from the DWV or regular PVC world.

Can you tell I've spent way to much time playing with the plumbing fittings?

[Jim Fisk]

Great job TC as always. A must read for anyone interested in AP.
Here are a few notes that I have learned over the past 2 yrs that might help people as well and compliment your work.

Sizing my pipes. A slightly different slant:-)
Starting at 1 1/2" pvc you have the option of sweep Tees which help keep flow going in the desired direction dramatically. Below that all you can get are 90 deg Tees which will restrict flow considerably by running into a wall. In my 5 full IBC FT and 15 GB 2000+gal system I use 1 1/2" S&D piping for the FT gravity flow waste water and have no problems at all.

I use 2" pipe (well vented with 3/4" pvc between each IBC GB in order to isolate the bell siphon from the drain by allowing air in just like the plumbing in your house) for the 5 bell siphon drains back to the below grade 275G sump and that has worked well. When completed this Summer there will be 3 such rows of 5 each having their own 2" manifold back to the sump for a total of 15 GBs. Personally I find that if you let the water slow down too much by using larger pipes THAT is where things can collect and grow blockages. ALSO by using the cheaper S&D (sewer and drain) pipe (unavailable in 2" for some dastardly reason) you get a great deal more volume for less $. 1 1/2" S&D is very close to 2" standard pipe in volume at about 1/2 the cost so I use S&D pipe where ever I can.

As to fish getting into the pipes
Here's how I make sure that never happens. I run a 1 1/4" id slotted pipe (approx. 1/4" slots along most of the bottom made on a chop saw) diagonally across the FT bottom and tie a 16" Walmart air stone on the top center (above the slotted area) using wire ties. Then a 90 elbow up the side to a Tee (which also acts as an overflow should the slots ever clog up) and out thru the FT side at the water level you want and on into the common gravity manifold heading to the GH grow beds. The air stone bubbles rising cause a strong up current that draws the fish waste on the bottom to the outflow pick up pipe below it. This keeps my FTs clean on the bottom as the trout stir things up on a daily basis AND keeps them out of the drain pipes. Works great.

Washing media right in the GB
I use granite gravel media and I wash the gravel right in the new GB by simply diverting the bell siphon drain away from the system until it runs clear. (one more reason NOT to glue everything) I use a hose from the well for wash water. Start by adding the gravel to one side and then move it to the other side thru the water filled GB and then let the bell drain the bed. I keep adding more and repeat and back again to the original side. Finally I add a 2" extension to the siphon stand pipe funnel and use the water level to level the media. THIS ELIMINATES having to move it all again. Works fantastic and granite BTW is very easy to wash and provides essential minerals to your system. Much easier than the river rock gravel I started with and better looking and about 1/4 the cost (18.00 a ton here and 1 ton fills 2 GBs to 12").

Don't cut the tops off those IBC FTs
By leaving the tops on the IBC FTs and cutting an access lid across the front I can fill to about 8" from the top so a 330g IBC will be about 300 gal without any fish (even trout) ever jumping out. Then I use a 275g IBC to make 2 GBs (the top and bottom) which works out perfectly per 330 FT. I start a 300g IBC with 50 trout fingerlings and since the growth rate ranges dramatically, by harvesting the larger fish first you end up never overcrowding and they can stay in the one FT for the duration (about a year). Moving and handling Trout can result in deaths from stress.

All my FTs are connected to a common drain at the 2" built in ball valve using a rubber "Furnco" connected to a 2" pipe manifold that goes out the side of the GH. Again use a sweep T at each tank. When I want to harvest fish I drop the level to about a foot (use a screen over the drain hole to keep the fish in) and then I net the big ones for dinner. Then I turn the water back on and let the tank fill again. DON'T forget to make up that water at the sump or your pump will shut down on the low water switch. AND YES you should always protect that expensive pump with a simple float switch.

Pump Head
One more note that people often misunderstand is that the lift of the pump should be measured from the surface of the sump water and not the pump itself. Until the water rises above the surface there is really no work involved. By keeping the sump as full as possible you increase your system flow accordingly and quite noticeably in my experience.

Folks can see most of what I describe here at my pics pages and at our IBC group and as always TCLynx has been my Guru from the beginning. When TC speaks I listen.

[TCLynx]

it's amazing how big a pipe you need to handle gravity flow.  My 300 gallon system uses 3" pipe as combined drains.  I have two separate lines, one for each side.  However that system has a trick up it's sleeve, on one bed is getting full flow at a time so the 3" drain is only getting a trickle from a couple beds while one bed might be at full tilt overflow so the 3" can handle that.  If I had a bigger pump and was sending full flow to all beds at once, I would probably be seeing issues with the 3" drain lines.

[steve]

Oooooh Tc, What hurt the most was being told ahead of time. I really did think the 3in was big enough for 2 separate drain lines. The 4 in I replaced them with was so much better. Nice when people share their mistakes and knowledge! Hope I don't have to repeat too many of the mistakes.                                                                                                         Plumbing and pipe sizes. Oooooh this is a stinger
So many people start their first systems with too small of pipe and find out later they should have used larger. Yea, the bigger pipe and fittings costs more but buying both the smaller stuff and a set of the larger stuff costs even more yet. Please remember that in Aquaponics there is this stuff we call bio-slime that can clog small piping. Algae can clog piping as well. For larger pumps, I'll connect the pump according to the pipe fittings the pump comes it. for small pumps, I now adapt up to larger pipe and I've found that a little tiny pump can sometimes actually move much more water than I expected. Even my ten gallon aquarium with a 20 watt pump is adapted up to 1" and 3/4" pipe.

[Ellen Roelofs]

A very helpful read - thanks!

[TCLynx]

Worm als help clean up old roots and other detritus that is never totally removed from beds when you harvest plants.

[Sylvia Bernstein]

good description TC.  Totally agree and that has been my experience as well.  I actually think a major key to not needing to clean out your beds is adding in red worms.  I'm convinced they do much of the poop processing for us!

[Allisyn Wood]

Thanks for the follow-up.  Looking forward to years of success :)

[TCLynx]

Granted I've only been doing aquaponics a few years so I suppose ti would be presumptuous of me to say a media bed is good to go indefinitely, however, there are people out there who have been doing aquaponics quite a bit longer and by accounts from many of them, they have had some media bed systems running for probably close to a decade without having to "clean out the beds and re-wash the gravel".  That said, in order for that to work, you need media that is not going to break down, you need enough grow beds that you won't be overloading them, you need some composting worms, and you need to not plant things that will block up everything with their roots.  I've never had a grow bed clog with fish poo but I have had a grow bed clog with mint roots or banana roots so beware the aggressive perennial plants.

 

Always make your drain plumbing accessible.  and if you need to glue all the gravity drains to keep them from getting knocked apart, at least give yourself a clean out some where (like a T to a thread on Cap that you could take off and run a snake through if you did get a clog.)  But for most of the plumbing you are better off oversizing things and you are less likely to get clogged.  Keep the leaves out of the plumbing if you can.

 

Anyway, There are some very eminent people out there that will insist that you need to clean your gravel out every 3-6 months to keep solids from building up but I've not seen it.  I've got some beds that have been running for years and I've never "cleaned" them  but I have lots of gravel in relation to my fish load and if I spread the solids out among the different beds, no one bed seems to get overloaded.

 

As to the flimsy bins, yea, few rectangular containers are really designed to hold heavy gravel/water and not bow out or bust.

[Allisyn Wood]

That's awesome!  I, too, particularly liked G.  My question is, do you have to occasionally completely clean out a media bed system, or really any system at that (ie: removing rocks, ...) or is it good to go indefinitely?  If it does require a major cleaning, how often should it be performed and is there a particular product that can be used in the PVC that's all glued together? I've just built draft 2 of my first media bed system (to the newbies: plastic tubs from the local hardware store will not hold water and rocks well at all without a major support and squeeze system also in place) and it was a PITA.  Wondering if this is something to look forward to on a regular basis.  Thanks for all the info so far.  Everyone is amazing on this site!