Sizing Grow beds

[Wayne]

I'm a little confused about how to size the beds for my system. I have seen a 1/1 ratio recommended for backyard AP, But also they recommend circulating all the fish tanks water every hour. I know it will depend on stocking density so lets say around 160-180 fish. I wanted to raise Tilapia but am considering catfish instead.

 

I have a 1200 gallon fish tank.

I guess my question is do you count the total volume of the bed or just how much water it actually takes to fill it? I have river rock for medium so for a 60gl GB it takes around 20gls to fill. 

 

What I had originally planned for was to have ten 60gl beds that flood and drain twice an hour. If you only count the 20 gallons it takes to fill them each time that would call for 30 GBs. 

Am I way off base or over complicating things as usual?

 

 

 

[TCLynx]

You simply want to make sure you are actually moving at least 1200 gallons of water per hour.  Don't worry to much about how much water it takes to fill the grow beds unless you are using some sort of controller that is going to turn off your pump as soon as the beds fill and then let them drain.

 

Figure out how many minutes per hour you are going to run your pump and make sure that pump will move at least the volume of your fish tank in that time.  I actually probably pump twice the volume of my fish tanks per hour.

 

If the water needs to flow over the tops of your grow bed stand pipes for several minutes on every flood cycle to get enough water flow, then so be it, the plants won't mind and the fish/water quality will benefit by it.

[Wayne]

Thanks TCL, I knew you would sound in.

So I will just increase the flow time to allow the tank to circulate. 

I am not too far along with building the growbeds to up size the drains. If I leave things the way they are I will be filling for 7-8 minutes, overflowing for another 10-12. 

It takes 5 minutes to drain, so that leaves 8 minutes at most before the beds would start to fill again. (Providing for two flood and drains per hour.) 

 

In doing the math again I have seriously undersized the new pump. I guess I can run the tank 1/2 capacity until the new beds are installed. 

[David Waite]

Wayne my system is 1000 gal and I have 750 gal of grow bed and 500 gal of raft tank. I can tell you that it will easily run another 500 gal of grow beds with about 100 fish. Things change as the system matures plants grow fish grow ect. I would recommend you have at least 1200 gal of growbed. This is empty volume. You could easily run another 500 gal of raft off your growbeds. Try to stay conservative in the start up. Use the standart 12 inch deep growbeds and plant the snot out of them. Start with no more than 100 to 120 fish. That mistake cost me about 300 smackers. Cycle your system fishless first. TC will walk you thru start up so pic their brains.

[TCLynx]

Biggest challenge will probably be sizing the holes in the bottom of the stand pipe so that your pump is able to fill the beds in the allotted time but so the beds are still able to drain.  If the bed only takes 5 minutes to drain?  I'm confused, are you running a siphon?  If you are running siphons, just let the pump run all the time.

[Wayne]

David,

Are you using one pump to run the beds and rafts? 1200 gal of grow beds, I have a lot of work to do. I think I will lower the level in the tank and cut back on fish for a while.

TC,

The original plan was to use siphons but getting them all timed right is proving to be harder than I thought. I think we talked about indexing valves a while back and I believe that would be a better option for my setup. I'm thinking (correct me please) that I can return the water back to the fish tank through NFT channels to maximize the growing space and take advantage of the already flowing (partially filtered) water.

 

I also like the split system David is using. I have the pumps excess water flow returning directly back to the tank. With so many options it is hard to remember the "KISS" rule.

[TCLynx]

Yes, always stop to think before you embark on a system modification.  "Will this improve system performance?"  "Will this simplify system Function/Operation?"  You need the answer to at least one of those to be Yes and hopefully you can make both of them YES.

 

Perhaps a diagram of the system layout or some pictures would help us visualize what we are trying to help you with.

[Wayne]

I will try to get some photos loaded.

[David Waite]

Wayne I am using one pump in my system. It is a 1800gph pump. I oversized it a bit for expansion. I use the extra for backwash which runs a venturi to inject air to the bottom of my tank. I pump into the gravel beds then the affnan cycle dumps the beds into the rafts. Each raft gets 100 gal of water dumped into them every 20 or so minutes. My third growbed dumps direct to tank. Definitely try to use either affnan siphons or a timed system. I like constant run it is easier on pumps but alot of aquapons swear by timed systems of 15 on 45 off. Keep in mind a index valve will not work very well with pond pumps because of the low pressure . They work really well with jet pumps or centrifical pumps which run at 45 to 75 psi. A pond pump normally gets to about 15. Hope we didnt overwhelm ya. Definitely take pics.

David Waite said:

Wayne my system is 1000 gal and I have 750 gal of grow bed and 500 gal of raft tank. I can tell you that it will easily run another 500 gal of grow beds with about 100 fish. Things change as the system matures plants grow fish grow ect. I would recommend you have at least 1200 gal of growbed. This is empty volume. You could easily run another 500 gal of raft off your growbeds. Try to stay conservative in the start up. Use the standart 12 inch deep growbeds and plant the snot out of them. Start with no more than 100 to 120 fish. That mistake cost me about 300 smackers. Cycle your system fishless first. TC will walk you thru start up so pic their brains.

[TCLynx]

I can help with pump sizing for indexing valves situations as I am near the manufacturer for the Aquaponics Indexing valves and have been working with them on low pressure applications.

 

Smallest pump I've managed with a gravity modified 1 1/4" indexing valve is the Quiet One 4000 pond pump with oversized plumbing and minimized pipe runs and head heights.

 

Otherwise I've been recommending the Danner MD18 (which is like a 30 gpm or 1800gph pump at 0 head) and it's been able to run all the Regular Aquaponics Indexing valves (which have the low flow stem disks) at about 3' head.  There is some trickle out the "inactive" ports but that so far doesn't seem to cause a problem as long as the flow out the active port is still plenty to flood the bed in the time allotted.

 

Of course now Rob has released a video of his motorized sequencing valve that can work on very low pressures since it doesn't rely on hydromechanics to seal the unused ports or work the sequencing.

Video

[Lonny Harper]

When sizing my tanks and growbeds, how do I calculate sizing my sump?  I'm going to use the Chop system.  Based on Dr. Lennard's excel program, I will need an 800 gallon fish tank with a density of 20 lbs per 250 gallons.  Does that mean I can have a 400 gallon fish tank and a 400 gallon sump tank if it is constantly flowing?  Or do I need a 800 gallon fish tank and an 800 gallon sump tank?  I will have approximately 100 sq. ft of growbed surface area...

 

P.S. along with that...how do I size my sump?

[TCLynx]

I have to admit to not being all that good with Dr. Lennard's program.  I think it makes things confusing when it tells you to up size the fish tank and then tells you that you don't need to pump that much per hour.  It isn't taking into account things like a CHOP system where the water level in the fish tank won't fluctuate.

 

How many fish are you planning?  You say 20lb per 250 gallons but how much fish total at grown out size?

 

Are you planning the 12 inch deep flood and drain media beds?

 

If the beds are flood and drain and 12 inches deep, then 1 fish per cubic foot of media is good.  Then you just need to figure out what the total volume of your grow beds are and then figure the sump tank needs to be like 60% of the total grow bed volume.  Figure the grow beds require about 40% of their volume to flood them once they have media and then you need some amount of water in the sump tank to deal with keeping the pump under water and dealing with evaporation and topping up etc.  I figure most people can get away with equal volumes of fish tank and sump tank and then have twice as much grow bed and still manage to make it work as a 2:1 system so say 800 gallons of grow bed to 400 gallons of fish tank and a 400 gallon sump tank and as long as you don't put any fish in the sump tank you have a functional 2:1 grow bed to fish tank system.

 

I'm not sure if this will help you figure out if you are on the right track or if it will just confuse you more.  100 cubic feet of grow bed will probably do well for you, but if you are only doing 100 square feet of shallow grow bed, I don't think it will work as well.

 

[David Waite]

Lonnie the rule on pumping in aquaponics is turn over the volume of water in Your fish tank every hour. In your case it is 800 gal. Here is the kicker. A 800 gal pond pump is at 0 head or lift. Also pumps lose massive amounts of efficiency when algae and slime coat the pipes. I recommend double your capacity to 1600 at least. I am using a 1800 gal in mine and could easily have gone to a 2500 to give more pressure to lift up to the top of grow towers and seeding tables ect ect....  In a chop you are also running the tank and the growbeds so I would definitely go 2000 gph minimum.