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 Post subject: New System Fish Question
PostPosted: Sep 10th, '17, 16:03 
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Hi all, this is my first post so allow me to introduce myself. I am John from South Africa.

I am new to this so please excuse me if I have said something wrong, I have also tried researching these questions on the internet and cant seem to find an answer for the system I want to use. I have recently found myself very interested in Hydroponics and decided to build myself a small gravity fed NFT system very similar to the image attached which I hope to grow 40 plants.

After doing a bit more research I have discovered Aquaponics and I feel that this is the way for me to go. Since I have already purchased all the PVC piping I want to know if I am still able to successfully grow via aquaponics on the gravity fed NFT system.

My second question relates to fish. Since my system is small I want to use goldfish. The system I want to use does not have a grow bed. How big does my tank need to be for 40 plants and how many goldfish do I need in a tank especially since I do not have a grow bed?




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PostPosted: Sep 10th, '17, 18:12 
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>> After doing a bit more research I have discovered Aquaponics and I feel that this is the way for me to go. Since I have already purchased all the PVC piping I want to know if I am still able to successfully grow via aquaponics on the gravity fed NFT system.

yes no problems. There are a few systems around like this, and a few more that use PVC pipes generally.

You will need to provide some biofiltration opportunity. This can be via media (media bed or a drum full of media) or a classic media bed using a trough or something.

> My second question relates to fish. Since my system is small I want to use goldfish. The system I want to use does not have a grow bed. How big does my tank need to be for 40 plants and how many goldfish do I need in a tank especially since I do not have a grow bed?

you passed the first test - least you didn't say 50 trout/tilapia/perch etc ;-)

Goldfish will be fine as they are much hardier and can get away with much less filtering.
You will still need some form of bio-filter - so a drum would work if you are short of space.
If you grow plants as a variety of sizes new to established (to suit harvesting) then you can probably get away with 10 goldfish.

** it more depends as much on what you feed the goldfish - flakes wont cut it.
** you would probably be limited to leafy greens (lettuce etc) without a decent nutrient source.

However the biggest issue is how big can your fish tank be ? You really want 200-400 Litres.

even if going with hydroponics I would have a drum - probably 50-100 Litres minimum.

I also wonder if your frame is strong enough.

See you have a timer - have you partially blocked the pipes to hold a bit of water or are they free flowing ?

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PostPosted: Sep 10th, '17, 21:24 
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Hi dlf_perth,

Thank you for your response.

Don't worry about the frame, mine is definitely much stronger than the one in the picture.

As for the system, it is partially blocked with a reducer On each end of the piping so there should always be some water in there.

How would I set up a bio filter? Is it just a small drum filled with perlite or something to that nature which water passes through before going back in to the tank? Would it not just be beneficial for me to rather create a system that passes water through the NFT set up which is then directed in to a grow bed or two?

Lastly are you saying that I can only grow leafy greens with an aquaponic system?


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PostPosted: Sep 11th, '17, 13:32 
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Have you built this system already Horsey?... If not, I wouldn't, until you've taken a few design aspects into consideration, the main one being the cascading design. In warm weather that creates a very effective heat sink, especially if you use a timer on the pump, which I wouldn't recommend. I would run the pump 24/7 and have an inlet into each level and separate drain from each level..
Horsey031 wrote:
Would it not just be beneficial for me to rather create a system that passes water through the NFT set up which is then directed in to a grow bed or two?
Yep!...

Quote:
Lastly are you saying that I can only grow leafy greens with an aquaponic system?
I think what dlf was saying, is that because of the lack of bio-filtration the safe fish stocking capacity would be extremely limited, meaning very little nutrient in the system, so that particular system, run in that way, would probably only be suitable for plants with very low nutrient requirements.

Lastly... I'm just nit-picking here and it's not aimed at you personally, you probably picked up the incorrect terminology from some youtube guru, I've seen it a lot lately... but that is not an NFT system.

NFT is the acronym for Nutrient Film Technique, a popular method used by commercial hydroponic lettuce and herb growers etc, where they use rectangular (cross section) pipe with a flat bottom, which the net pots sit on. The lengths of pipe are placed on a slight incline and a fine film (only mm or two) of nutrient solution runs downs the length of the pipe, just contacting the base of the net pots.

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PostPosted: Sep 11th, '17, 20:29 
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Would it not just be beneficial for me to rather create a system that passes water through the NFT set up which is then directed in to a grow bed or two?

the other way around. It would be better to go to a media bio-filter/bed and then on to your tubes via a sump.
(pump from the sump and the pipes can feed to the fish tank).

Lastly are you saying that I can only grow leafy greens with an aquaponic system?

Aquaponics can grow many things but it all comes down to the nutrients (as Mr damage notes).
10 goldfish in small system will keep you in lettuce/rocket, cress, herbs like basil but not more demanding vegies.

If you went to say 400 Litres then you could increase the number of *larger* goldfish (they don't take long to grow in the right conditions) and get then some additional benefit as your system matures.

The pictured PVC setup would suit lettuce and leafy greens/herbs, maybe strawberries, but not anything heavier than that.

Mr damage made a good comment here (and the picture is the good reality check)... viewtopic.php?f=12&t=29072

There are some good small rubbermaid type systems in the forum and they would be a good entry size.
search rubbermaid.... most will be quite sobering compared to the promises of YouTube videos. These are real systems run by real people. You can fake an AP system by using lots of foliar feeding or liquid seaweed additives - and that is definitely an option if you run a low fish density (I do this myself for tomatoes and other heavy feeders).

The potential for a small system is shown by Dangerous Dave...
viewtopic.php?f=18&t=22374


I run a series of 5 tanks 500-800L. One of these is 500L system in 3m x 0.6m (10" x 2-3") with 10-15 medium sized goldfish and it drives the equivalent of 2-3 x 100 Litre (25-30 Gal) tubs of media, plus a tub DWC with 14 plants. I use Seasol (liquid seaweed fertiliser), bit of iron and the odd addition of blood&bone to the media.


--------------------------------

> How would I set up a bio filter? Is it just a small drum filled with perlite

definitely not perlite. The simplest is a drum or half drum (around 100L minimum) filled with inert coarse gravel around 5cm (not limestone) or clay balls with an inflow to the bottom and an outflow. I have done that where I had a shortage of room and needed some biofiltration volume.

Or you can just go with media beds and grow stuff in them.

Or you can go complex with drum filters, bioballs or bottle tops etc etc

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PostPosted: Sep 11th, '17, 21:30 
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Thank you for the advice. Now I have even more question...


Have you built this system already Horsey?...

I have not built this system but I have all the supplies which cost a fair amount. I really would like to use what I have if possible. I can understand why the cascading design would cause a heat sink in warm weather but could you elaborate on why this is a problem? Is it because it affects the water temperature the fish are in? Is this really a big factor I need to consider or can I get away with my current design? Perhaps I could paint the tubes black? to attract heat since I will be putting this outdoors?


Lastly... I'm just nit-picking here and it's not aimed at you personally, you probably picked up the incorrect terminology from some youtube guru, I've seen it a lot lately... but that is not an NFT system.


Thanks and noted. I most likely did pick this up from somewhere on the internet since I am new to this.


the other way around. It would be better to go to a media bio-filter/bed and then on to your tubes via a sump.
(pump from the sump and the pipes can feed to the fish tank).


I did not think of this but I could probably do this with a simple design change. Could you explain why this would be beneficial? Would this be the fish tank moving water to the bed via an overflow > water moves through the grow bed and feeds in to the tubes > water flows in to sump tank > pump moves water back in to fish tank.

If you went to say 400 Litres then you could increase the number of *larger* goldfish (they don't take long to grow in the right conditions) and get then some additional benefit as your system matures.

Currently I can get free 210 liter plastic barrels that I want to put on its side and cut a hole in for the fish. Would it be possible to use two or 3 of these tanks? I am also thinking about building a small pond by digging a hole and using pond lining or look for a 400l tank.

Lastly from the size of my system would you rather recommend I stick with aquaponics (and grow my system if necessary) or make a move to hydroponics.

Once again thanks for the help. I really do appreciate the advice.


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PostPosted: Sep 11th, '17, 22:11 
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There are blue barrel systems around in both the vertical and on side.
To get fish to a larger size however you generally need the space/volume in X-Y rather than height.

The fish water is ammonia rich and has solids etc in it of various types (algae as well as fish poo).
quasi NFT-shallow DWC etc need filtered water. So you go out of the fish tank into your media container and then from that on to your DWC etc.

A lot of PVC based systems run horizontal. This can work a bit better and requires less pump energy.
Andres (DasBoot) had one in his early setups (one pic on page 6) > viewtopic.php?f=18&t=16235&start=75

If you can locate an IBC they make good fish tanks at whatever height you like (500L up to full IBC with no top = 900L.
Else you can use the pond liner. Or any other suitable tub or rainwater tank etc..

A simple media drum would be something like this... This style (below) is a top overflow and thus you don't lose too much height. In this setup you collect the solids etc via the bottom - so its easy to flush..

Attachment:
DF_Simple Media Drum Filter.jpg
DF_Simple Media Drum Filter.jpg [ 29.8 KiB | Viewed 409 times ]


if you played around you could pretty much feed a ring of water at the top and pump direct out of the bottom using a 90mm pipe in the centre. But I would probably use two drums and have the pump in the second. It would work with an airlift pump or a simple pond/fountain pump.

But it would still be a limited system since the volume of wet media and number of fish is still going to be small unless you can get up to 500 Litres plus.

It may be worth you having alook at the FAO Small System Aquaponics edocument.
It will explain quite a few things for you. Google this for PDF links > FAO small-scale aquaponic food production.
else try this > http://www.fao.org/3/a-i4021e/i4021e19.pdf

but similarly (to provide all options) you could use a drum upright or on its side and stay with a hydroponics approach and no fish.

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Last edited by dlf_perth on Sep 11th, '17, 22:22, edited 1 time in total.

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PostPosted: Sep 11th, '17, 22:20 
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Horsey031

I don't see that you got a specific answer to setting up a biofilter. There are a lot of examples available.

Hears a pic of the one I used in my basement system.

The tub is a mid size PVC faux wine barrel that I drilled to add:
C) an overflow, just in case inflow exceeded outflow at some point piped back to the FT)
B) a siphon flow drawing from the surface of the barrel (piped to the GBs), and
A) spigot to allow for pulling excess waste out of the system via a bucket which I could add to my compost (I only did this twice during my early cycling, after that the bacteria caught up).

1) The pot on the right is pond gravel I used as substrate. It was from an outdoor pond established over 3 years and had a good population of worms, daphne, etc. this went in the bottom of the barrel.

2) On the left is a bunch of mesh (from an old formal gown) which went above the gravel.

I grew out 7 Blue Nile tilapia fingerlings and successfully bred them this spring. This week I will fillet the breeders and start resetting my basement set up to grow out my fingerlings for spring harvest and early summer breeding. My system is small as I'm only raising fish for friends and family.

Good luck with your system.


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