Backyard Aquaponics
A place to discuss aquaponics

As I understand it, most any plant will grow fine with its roots continually submerged in water if the stem is somehow kept out of the water. If true, why use a growing medium ?

zkt

Some people don't use a growing medium, and have the plants in sheets of styrofoam with the roots trailing in the water.

I think one of the main reasons to use growing medium is filtration. The solids are removed from the tank, and the growing mediums surface area is colinised by nitrifying bacteria.

Others may have different reasons....

another reason is plant support.
I grow strawberrys in foam, but try growing tomatoes.

THe support and surface area for bacteria are both very important indeed - as is the physical filtration of solids...
Some systems have run for 2 years with solids from the tank being pumped in (in a flood and drain system) and there is almost no sign of the vast amounts of solids when the bed is checked after the 2 years - it breaks down, is eaten (earthworms seem to like living in the growbeds) and is absorbed by the plants.
For me its important to supply as much surface area for the nitrifying bacteria, as the system revolves around them removing/breaking down the amonia and making it avaliable to the plants as a food source.

Yep for the filtration and bio is why I'm going with gravel and the added bonus of getting to wash rock.

Same, gravel is my choice aswel. and Yay washing rocks!

with or without your sexy rubber gloves?

gravel was my choice also

LOL - even expanded clay balls need a very good wash (unless you like the red/pink look to your tank/pond

Might be a silly question, but I thought earthworms drowned in water? Do they actually survive in flood and drain gravel beds?

Wow, another possible home for my gorgeous invertebrate pets........

Melinda

It's all about the oxygen Mel. Plenty of oxygen in the flowing water and they won't drown

Yep, I threw a handful into my barra system a while back and they were still alive 2 weeks later (unser some bits of old pots)... A high DO is a must in that case... I have earthworms in all my beds (continious flow) now and they are doing well.

I`d have never thought that earthworms conud live under water. The convertional wisdom has been that they come up out of the ground when it rains to avoid drowning. Seems like theyre would be plenty of DO in rain water. Soudns like a job for The Mythbusters. LOL

At first there may be a fair amount of DO, but that is quickly used up and is not replenished - in AP there is an uninterupted flow of water, so DO remains high

I have a bit of grass growing underwater in a system, seed got lodged in a bit of scoria I put in there I'd say.

who nneds DO meters - that is enough of a good indicator I'd say!