failure

and

if

not


rectified


or


previously


prepared


for,


loss


of


fish

stock


and

veggies


is


likely.
Like

all


aquaculture


based


systems,


stock


feed


usually

consists

of


fish

meal


derived


from

lower


value
species.

Ongoing


depletion

of


wild


fish

stocks


makes


this

practice


unsustainable.


Organic


fish

feeds


may
prove

to


be

a

viable

alternative

that


negates

this

concern.


Other


alternatives

include

growing


duckweed
for

fish

that


consume

vegetable


matter,


excess

worms


grown


from

Vermiculture

composting,


as

well


as
growing

Black


Soldier

fly

larvae


to


feed


to


the


fish.
Types

of


Aquaponic

Cultures
The

two

main

types


of


Aquaponics


are


water


only


culture


and

medium

culture.


The


water


only


culture


does
not

use

a

solid

medium

for


the


roots,


just

the


effluent


water


from

your


fish.


The


two

main

types


of


water


only
culture

are


continuous


flow


water


only


culture


and

Aeroponics.


The


medium

culture


method


has

a

solid
medium
for


the


roots


and

is


named

for


the


type


of


medium,


e.g.


sand

culture,


gravel


culture


or


rockwool
culture.

There

are


two

main

variations


for


each

medium,


subirrigation


and

top


irrigation.


For

all


techniques,
most

Aquaponic


reservoirs


are


now


built


of


plastic


but


other


materials

have

been


used

including


concrete,
glass,

metal,


vegetable


solids

and

wood.


The


containers

should


exclude


light


to


prevent


algae


growth


in


the
effluent

water


solution.
Continuous

flow

solution


culture
In

continuous


flow


effluent


water


solution


culture


the


water


from

your


fish

constantly


flows


past


the


roots.


It

is
easy
to


automate

because


sampling


and

adjustments


to


the


temperature


and

effluent


water


can

be

made
easily.

A

popular


variation


is


the


effluent


water


film

technique


or


NFT


whereby


a

very


shallow


stream

of


water
containing
the


effluent


water


is


re

-

circulated


past


the


bare


roots


of


plants

in


a

watertight


thick

root


mat,


which
develops

in


the


bottom

of


the


channel,


has

an

upper

surface


which,


although


moist,


is


in


the

air.
Subsequently,

there


is


an

abundant


supply


of


oxygen


to


the


roots


of


the


plants.


A

properly

designed

NFT
system
is


based


on

using


the


right


channel


slope,


the


right


flow


rate


and

the


right


channel


length.


The


main
advantage
of


the


NFT


system

over


other


forms

of


Aquaponics


is


that


the


plant


roots


are


exposed


to


adequate
supplies
of


water,


oxygen


and

effluent


water.


In


all


other


forms

of


production

there


is


a

conflict


between


the
supply

of


these


requirements,


since


excessive


or


deficient


amounts


of


one

results


in


an

imbalance

of


one

or
both

of


the


others.

NFT,


because


of


its

design,


provides


a

system

where


all


three


requirements


for


healthy
plant

growth


can

be

met


at


the


same


time,


providing

the


simple


concept


of


NFT


is


always

remembered

and
practiced.

The


result


of


these


advantages

is


that


higher


yields

of


high


quality


produce

are


obtained


over


an
extended
period


of


cropping.


A

downside


of


NFT


is


that


it

has

very


little


buffering


against


interruptions


in


the
flow

e.g.


power


outages;


but


overall,


it

is


probably


one

of


the


more


productive

techniques.
The

same


design


characteristics


apply


to


all


conventional


NFT


systems.


While


slopes


along


channels


of
1:100

have

been


recommended,


in


practice


it

is


difficult


to


build

a

base

for


channels


that


is


sufficiently

true


to
enable

effluent


water


films

to


flow


without


ponding

in


locally


depressed

areas.


Consequently,


it

is
recommended

that


slopes


of


1:30


to


1:40


are


used.


This


allows


for


minor


irregularities


in


the


surface


but,


even
with

these


slopes,


ponding

and

water

-

logging


may


occur.


The


slope


may


be

provided


by

the


floor,


or


benches
or

racks


may


hold


the


channels


and

provide


the


required

slope.


Both

methods


are


used

and

depend


on

local
requirements,

often


determined


by

the


site

and

crop


requirements.