Backyard Aquaponics
A place to discuss aquaponics

Lets see, the only media I have used thus far is a 8 to 10 mm gravel called Tinaroo gold...
Pro
Cheap, but could be cheaper (it is used on paths and in potplants as decoration).
It has not affected the PH of the water at all.
It is free draining (there are very few small bits in it to clog up the works)... All my plants in my grow beds seem to like it / seem to be happy, as are the earthworms I added as an experiment a month or so ago.
Con
It is rough on the hands and once a growbed is filled with it , it is as heavy as all hell!
There is a lot of very fine dust which takes a lot of washing to get rid of.

Hydrotron or expanded clay balls

Very light

very expensive

large surface area

approx 80% will sink after being water logged for a time. The rest still float and may be an issue for flood and drain

Need to be washed as they run red from the dust.

Hydroton--and it still floats after more than a week, good point, noticed that water migrates easily so have reduce the amount of water to avoid floating.

using the expanded clay balls, I run a continual flow system so don't have the floating issue.
As stated expensive but light and easy to handle good for bacterial growth and readily available.

The con is very much the price and the initial flush or red dust into the water, I have a picture of one of my tubs after the adding of the clay without cleaning.

yeh how is that, happened the other day three ponds went red aaarrggg, but tis all good now.
I forgot to wash I was in a hurry, learning not to rush as much now.

Gravel

Pro:
I can get 25 gallons of 1/4" pea gravel from the local sand and gravel place for $2.
It is heavy enough to keep the plants anchored on breezy days, but probably not enough for really windy days (depends on how tall the plants are and the amount of wind, mine hasn't been tested yet).

Cons:
It is heavy.
You have to clean it before use.
My 9" shallow rectangular tub is not draining fast enough to keep up with the pump. The topmost gravel wasn't cleaned of sand. This, the shallow depth and the little slits in the standpipe are combining to cause this drainage problem. I haven't seen drainage problems dut to root growth yet.

once again gravel....

Pros
cheap (i got "bean gravel" @ $65 a tonne)
wont float away
Smooth, so gentle on the hands and wont scratch up your grow beds
did i mention cheap?

cons
not as good surface area for bacterial colinisation per volume
heavy
needs to be cleaned (but it looks like most do anyways)


and prob some others i havent thought about yet

scoria i went to the garden supply today $40.00 a cubic meter see its mined not far from here as for washing 1/2 meter in the back of the ute and hit it with a fire hose all the dust washed out easy

I have been using pea gravel and shell grit to increase the water hardness. (Tilapia and the Malawi cichlids like hard water).

shell grit will increse your carbonate hardness and as a result buffer the PH of your system VERY well (you probably already know this)

Why use growbed media?

A. Support for the plant. The plants roots anchor to the media to support in windy and rainy conditions.

B. Allows the plants to take up O2 and exchange CO2.
The main supply of oxygen for the roots comes from the air in the voids between the particles of media. In flood and drain systems, the draining of the growbeds draws air down through the media. Dissolved oxygen is also present in the water. The plants roots give off CO2 which is toxic to the roots so good aeration is important.

C. Helps to maintain even root temperature.

D. Allows the uptake of nutrient and water.
Note: The media may be dried out to stress the plants in order to stimulate flowering and fruiting. (but not to long to stress out bacteria)

E. Allows surface area for bacteria growth.


Particle Size of Media.

The larger the particle size of the media the greater will be the amount of root aeration. However the larger it is the lower the amount of the nutrient rich water held around the particles & between the voids..(hence quicker drying..ie large size gravel.rocks).

If the particle size of the media is small then it will have poor root aeration but much higher water-holding capacity (take longer to dry out..ie perlite/vermiculite).

If you have a mix of coarse & fine media then the fine media will fill the voids between the larger particles resulting in poor root aeration but better water holding capacity..(with a very wet bed there will be an increase chance of fungal diseases).

The most acceptable particle size for media seems to be 8-10mm.

Media I have use!

Gravel (crushed rock) - Cheap, builds big forearms.
Scoria - Cheap, Good surface area.

Who has used these?
any info for us?

Rockwool can get rotten spots and alter pH. No thanks. No experience with others I'd never touch rockwool again it was not an isolated incident.

I've priced some gravel from the suppliers (relatives who will give me mates rates). Now if possible I'd like some feedback from all you experts on which would be the best one for us. Please...


The first one is screened gravel from creek sand. Not exceptionally rough or smooth.

The second one is crushed granite. Fairly rough edged stuff, very angular.

The third lot is kind a mix of the two.

By price preference, I like the screened gravel.

What advice can I get on this from the experts?