Backyard Aquaponics
A place to discuss aquaponics

Hi everyone !

I'm thinking of building my first aquaponics system in about a year's time, after my upcoming move to Washington state. I have the design more or less decided, and had some questions about water flow rates.

I'd love to have a couple of 4 inch PVC pipes that will hold a bunch of herbs, strawberries, etc., which will be fed by water from the side of one PVC pipe, and gravity will help it through the pipes until it drains into a growth bed, which will have a bell siphon. I'm going to automate a pump that will pump water until the siphon triggers, and then shut off - it'll probably wait about fifteen minutes and then start again. The system, therefore, has a nutrient film technique that keeps the herbs going in their PVC pipes, and a flood-and-drain setup for the static grow beds.

I'm a little worried about water flow. If I pump the water into the PVC tubes, how much water needs to be in them to correctly keep the roots nourished ? The videos I've seen show them about half-filled. Can I readily keep them half-filled whilst still correctly draining into the growth bed ? Should they empty completely, or still half-filled at the minimum, during drainage ? Basically, does NFT require more water flow than flood-and-drain ?

Also, if anyone has ideas on how much this type of system will rob my growth bed of nutrients because they're taken up by the PVC pipes, that kind of information would be great !

Thanks very much.

Welcome to the forum Skei

You might need some filtration in front of the pipes. Solids can smother the roots.

If you ran FT --> GB ---> sump (pump location) ---> plant pipes then back to FT, that might work better. There are a number of systems where people have grown in Pipes and you may want to look around for those and check to see what worked for them.

Cheers

Basically, does NFT require more water flow than flood-and-drain ?

No,NFT is a constant flow system with flow rates in the 1 litre per min range,water depth is no more than a couple of mm in the bottom of the gully,tubes are different as the film of water is narrow so more water depth is an advantage.

Thanks, scotty435 ! I was thinking of having a swirl / spiral filter before the plant pipes to take out the sediment, although maybe the grow beds will do a better job filtering, and should therefore come before the plant pipes. It's a shame, I wanted to have the plant pipes above the grow beds...

dasboot, thanks - good to have a general idea of flow rate. Maybe I didn't mean NFT then ? A large number of plant pipes systems I've seen are basically half-filled with flowing water. I'm not sure if this is a good idea, or good for the roots. I'll keep looking up different systems to see if I can figure it out. Thanks.

I think you might be able to pull this off but I'm not sure. I used to have a hydroponic setup with towers above a flood and drain table. I was able to pump to both at the same time and the towers drained to the tray. It might be a bit tricky depending on the piping and the pump but it's definitely a possibility as long as any water that comes to the towers has gone through the grow bed or filtration. There is a down side to having the towers above the grow bed - sometimes splashes or drips on plant leaves can allow disease problems to get going.

Skei, Why not gravity feed to your grow beds and allow that supply line to continue on and become your NFT? That is what I am planning. That way you can put a ball valve at the end of your bed and just before your nft and at the end just before going into the sump. That will allow you to control depth so higher with younger seedlings and lower with mature plants. I would consider running timer 24/7 with your bell siphon that way your nft is running constantly and less chance of any build up in the tubes.

Scotty, thanks for the insight. I could certainly think about pumping to both simultaneously. I was hoping for something a little simpler, but that might well solve the issues. Do you think a sump is absolutely necessary, or is a swirl filter and the grow bed enough before sending water into the pipes ?

Garyjr, thanks for the thought. I'd come to a similar idea - the only issue is aesthetics, I guess. I'd like the fish tank below, as I don't think I'd make it very pretty ( just an opaque container, I'd guess ), with a grow bed on top at the right height for planting and such, and the pipes above because things would be in little net pots and easy to manipulate that way. To allow the grow bed to drain into the pipes, the bed would need to be raised higher than the pipes, which is a shame. It also means that the bed would not be able to be flood and drain, in order to get continuous flow into the pipes - that, or there'd need to be a sump tank in between, in which case I might as well go with
Grow Bed > Sump ( pump ) > Pipes > Fishtank
Then the fish tank would be raised above the grow bed, to allow that to go with gravity too. Hmmm, could work, depending...

You don't need a sump if the water comes from a higher location than the NFT since it sounds like water will be flowing by gravity to the NFT system from either a grow bed or swirl filter. Either the grow bed or swirl filter is probably enough but I"m not 100% certain on this. Some of the people here that run NFT can give you a better indication on this. You might need a fines filter.

Hi Skei
My ten cents worth.
Forget NFT. As DB said you are looking for flows of 1lt/min. Truly a film of water. DIY square tubes are a nightmare. One tiny leak with constant flow is a major problem. They will act as a major heat exchanger. Temp control and fish species choice is critical.
Availability will vary with your location but I would suggest the following.
110mm round pipes. Drill holes to accept 7.5mm media filled net pots.
Use 22mm pipe to connect subsequent tubes via gravity flow.
Drill the hole for the 22 mm pipe towards the bottom of the end of the big tube end caps. Incorporate a moveable , ”L” inlet. This will enable you to control the water level in the 110mm pipes.
I would run this as a separate dedicated system. Pump from sump ( choose smaller pump to suit) bottle top Up-flow filter to remove fines and return to FT and thus join main system.

Titus hope you dont mind me using your post but its how i would do with just one small change.

The major heat exchanger +1

110mm round pipes. Drill holes to accept 7.5mm media filled net pots.

Yes,you could even grow Toms in that at a push,7.5mm bit small for a pot Titus...

Use 22mm pipe to connect subsequent tubes via gravity flow.

Now i wouldn't do it this way personally,i would use a separate feed and outlet for each tube,that way when an inlet blocks its just one tube,plus i would be concerned about oxygen levels if i was running more than just a film of water in the tube

Drill the hole for the 22 mm pipe towards the bottom of the end of the big tube end caps. Incorporate a moveable , ”L” inlet. This will enable you to control the water level in the 110mm pipes.

I did something along those lines,i had an offset reducer which wasn't glued,it was quite easy to rotate it to increase or decrease levels,in combination with the run you put on the tubes.

I would run this as a separate dedicated system. Pump from sump ( choose smaller pump to suit) bottle top Up-flow filter to remove fines and return to FT and thus join main system.

Yes i used Bio Balls and shade cloth and a 20 watt pump,for 6,2metre tubes and 5 3meter tubes,i have a two tube strawberry NFT now running with a 7 watt pump.
I ran a 6 tube NFT using the bottle top upflow,it kept the tubes remarkably clean

Hi DB
Distracted by that wonderful shot of the saloon in you NB.
No worries!
7.5mm net pots? Micro greens!
Some of my post was personal thinking.
Skei, Please forgive me if I digress from you original question.
Last year, on my square line NFT I used a 22mm manifold. This fed four 10 mm outlets. Uncontrollable variable flow.
I added four 10mm valves. Daily variations requiring constant adjustment.
The real problem was getting square tubes 100% watertight.

I digress but the root structure of a lettuce in a true NFT is a wonderful thing to see.Imagine a pure white herring bone patten. 1mm high but up to 20 cm from the plant.
Sometimes the pure symmetry of nature leaves you speechless.

After two tubes of fish safe silicone I gave up.
I have no space for expansion.
But.
My neighbor has said that I can fix tubes to my shed wall and go into her garden to work on them. Summer months only.
The shed wall has summer afternoon sun only. Not ideal.
The plan is three 3 mtr 110mm tubes at 50cm vertical intervals.
I am hoping that the 50cm drop will overcome the oxygen depletion you mention DB.
Use the movable “L” to vary water height but in all reality 1 to 2 cm so not true NFT. Carp in the main tank so I can cope up to 30*C ( I wish)
I said 750 mm holes because that is the size of the biggest hole saw I have.
Now I am obsessed with watercress. So that will be the main crop. Possibly also some Venlo cucumbers for pickling
Copper tape at regular intervals to deter slug/snails.
I am also considering companion planting.
Tumbler F1 are a trailing (non side shooting removal) cherry tomato.
Marigolds are a great accompaniment to toms. Keep away the tom hungry insects.
If I plant the marigolds and Toms to form the initial letter of her name I might get a second season.
Mrs Titus has fully approved this message!

I think I misused the term NFT, as clarified by dasboot. What I meant was really circular PVC pipes in which I'd drill holes large enough for net pots.

Titus : thanks, I like your earlier idea, with round PVC pipes ( though I might still try to incorporate it into a single system, with enough valves to control water level ). Do you know what kind of flow rates are good for this kind of system ? Do I need to drain the water regularly to let the roots breathe, or are the pipes always more or less half full ?

Dasboot, scotty : thanks for the input, very helpful

I think I have a vague idea of where I'd want to take it. ETA : several months, as I'm moving to another country first...