Backyard Aquaponics
A place to discuss aquaponics

Greeting fellow aquaponic-ers!

My brother and I want to set up a big aquaponics system...We have unlimited space and fresh water. I just had a few quick questions regarding the actual water delivery system to the plants.

Firstly, PVC pipes are realtively cheap round here, I thought I'd use them for the grow beds. I would cut off the top, leaving uncut sections every so often to add strength. My principal question is wether making and NFT system with gravel is possible. I want to make it an NFT system because the flood and drain method seems rather complicated on a large scale. Furthermore, it would provide constant oxygen for the fish. I would not pump too much water through the system, just leaving the gravel constantly wet on the bottom.

Secondly, how much space is necessary for roots? Lets say, space enough for a cayenne bush. Would a 100mm pipe be enough? Or a 150mm? 150mm are alot more expensive than the 100mm...

Here is a more or less diagram of what I want to do. TCLynx has given me some tips, such as adding a sump tank(I think you call it). Thank you all very much in advance!!! Hope to hear from you soon. Cheers dudes!!

Greetings,
The biofilter needs to be before the grow beds, otherwise your grow beds will be the biofilter.
So, were it my system: FT to solids removal to biofilter to growbeds to sump (if required as depends on levels), then back to FT clean and filtered.
Solids removal via settling is easy, biofilter can do double duty and oxygenate the water. This keeps the gravel beds clean and eliminates the potential for dead/anaerobic/toxic spots. You will find there are two camps in domestic AP systems, the filterers and the 'let it all go through the beds people'.

Gravel in flood & drain growbeds or an external filter before your NFT... no problems...

Gravel in your PVC pipes with a continuous... big problem... everyone that's tried it has reported the roots block the pipe in no time... and gravel makes it almost impossible to get them out without cutting the pipe...

IMO... you also run the risk of channeling, leading to dry spots... root rot... and possible anerobic zone formation...

NFT... stands for "nutrient film technique".... i.e a constant "thin" film of nutrient rich water...

I think you need to do a lot more reading about the various styles of aquaponics and the pros & cons of different methods..

I like your ideas of different species fish tanks but like others have said. Flood and drain makes things simple.

Actually, if you do a good job of solids removal, say a settling tank/system, then a net filter, degas, oxygenation, etcetera, there is no reason why a gravel bed can't be continuous flow.

Here's a question for the learned; why aren't continuous flow gravel grow beds used? Take something like Earthbound's raft system, and fill the DWC with 20mm smooth river gravel instead of rafts - why is this not done? No solids would be flowing through the system to clog it up, so what's the probelm(s)?

In a nutshell .... oxygenation... that's why even UVI raft style systems are heavily oxygenated within the raft beds...

Flood & drain systems redress the problem by nature of their design. And there are a few members that have, or are running continuously with bell siphons which acheive a similar oxygenation... and a very few that have managed to highly oxygenate their water and use a continuous flow methology... with reasonable results...

However in the most part, those that have tried it have found that the results have been poor in comparison to flood and drain media beds... and have exhibited problems in the long term with clogging, anaerobic zones, poor water quality and even complete disasters...

And most of the time the purpose of Floating raft is to reduce the labor involved in planting/harvest. Adding gravel that needs to be dug kinda negates the labor savings of doing floating raft. Also, floating raft systems tend to be very extensive and the cost/weight of gravel can become prohibitive.

The benefit of flood and drain gravel beds is that they can act as solids filters, bio filters, plant growing space/support, and provide the extra aeration needed for their own operations without an extra air pump.

If you are going to be adding solids filters, and bio filters anyway, then why bother with the gravel beds at all unless it is just to be able to grow large plants that need the support?

Constantly flooded gravel beds can be done (I believe Creative1 does it that way) but one must keep in mind the limitations of such. The amount of gravel needed to support a given weight of fish is different than the numbers we usually use for flood and drain gravel beds.

Here is the diagram I recommended to adjust the arrangement.

too true TCL
Not sure of the limitations of it either
very happy with the results so far...
The 150 trout are growing nicely
and will not be far away from having a sample
I didn't want to bore anyone with pics

So the bio-filter is for the plants? And then the gravel grow beds act as a biofilter for the fish? And that secondary tank would be the "sump tank" Is that right?

I think I am going to flood and drain it automatically. Let the pump run continuously to provide air for the fish, but when I want to flood the beds, just open a valve. Constantly flooded isnt such a good idea I guess. I would also major on spices and veggies. Thanks dudes! Tell me what you think

Woops, I meant flood the beds manually hehe

The system all works together as a balanced system. The bio-filter is to change ammonia into nitrite and then into plant usable nitrate. Both ammonia and nitrite are dangerous to fish. Nitrate only becomes dangerous to fish in very high amounts but plants can use the nitrates so the plants help clean the water for the fish but the bio-filter is also to help both the plants and the fish. The solids filter is needed if you are not using flood and drain gravel beds since most separate bio-filters don't do as well with extensive amounts of solids and most NFT or DWC plant growing suffers if there is too much solids in the water.

If doing NFT pipes for your plants, you are probably better off letting the water run to them all the time.

I think you do need to do more reading and research before settling on a particular method.

I personally like the NFT technique as it fits my applications. But definately listen to those saying you need a biofilter before the water reaches your channels. If not you will see the solids inhibiting your growth and causing rot. Also, make the biofilter much bigger than you think it needs to be and monitor it closely. For my exhuast/return manifolds from the tubes I use tubing which can be adjusted for height, this way, when net pots are first introduced with rockwool germinated plants which don't have long roots, I can raise the level of water in the tube to make sure the roots are getting nutrients, then lower the level as the roots grow. Good luck looks exciting.

Elston, having variable water level in the NFT channels is very intriguing to me. I would very much like to see a diagram or picture of the adjustable return manifold...

Rick

Very nice. I wondered how you could get started with shorter roots. I saw a small system with net pots full of clay pellets that wicked the water from the bottom of the tubes to the roots further up. Then the roots grew down and out of the net pot of clay pellets. Your approach of tilting the angle to adjust water level in the NFT pipes is very interesting. Anything else to say on that?

There is a good discussion of factors in NFT AP in a book I just read. It is "Aquaponic Food Production" by Rebecca L. Nelson which can be seen at www.aquaponics.com. The concentrations of nutrients are different than Raft or Flood-Drain and the ratio of fish/plants is different on the order of 4 times the plants for the same number of fish. Water temperature and oxygen depletion increase down the length of the channels. The monitoring of system parameters is more critical according to what I read in this book.
Good luck and please keep the group informed of your progress. Perhaps seperating the system into smaller modular units would allow you to do more testing and tuning and prevent a total loss due to one problem developing.