Backyard Aquaponics
A place to discuss aquaponics

I must start growing some again. Once I have transferred my fish into my Murray tank I will use one of the ponds to grow duckweed. I let my main supply die - but luckily there were a couple of pinhead sized bits left in my aquarium after I took the perch out - and this has now bred into enough to start a new batch :-). I recall from previous discussions that the duckweed likes to take the ammonia first, but will after that extract nitrate. Do I recall correctly. Do we know how much nitrate it would take out - I am assuming less than what plants would from an equavalent sized surface area grow-bed??

I have a really good supply of duck weed now growing in my front yard pond. When I went away over Christmas I took 10 litre bucket full of duckweed out of the front pond and put it in the fish tank to feed them while I was away. This worked well for the fish. The duckweed covered about 90% of the surface of the tank. I have left it in there this last week and also fed the fish a small amount of pellets just once a day.
I have just this morning scooped out all the duck weed as I feel that my grow beds are suffering a bit, I feel that the duckweed is sucking a big hunk of nutrient out of the Fish tank before it gets to the grow beds.
I really must buy a nitrate test kit. (or invite VB over for coffee and get him to bring his test kit)
If I had a test kit then I could be exactly sure about this.
By observation, the duck weed in the fish tank has a much greater number of young compared to the duckweed that has remained in the front garden pond. The duck weed is doing very well in the fish tank. Gary D or VB made the observation that Jades and Silvers only eat what they need, and I can agree with that....I can see a situation where the duck weed would entirely feed the fish and the duck weed would be sustained by the fish, if you wanted to raise only fish.... might be worth a try.
So it is reasonable to assume that too much duck weed on the surface of ones fish tank is not good for the grow beds .....
Anyone else had experience with this ? If so what are your observations.
Muzza www.aquaponics.net.au

I intend using one of the sump tanks to grow duckweed (and toss some redclaw in), will keep notes on how that experiment works.

Time to get some duckweed now as the ammonia is zero and nitrite levels in decrease mode - anybody got some spare duckweed going to Gary's

Some of my thoughts:

1. Duckweed taking nutrients from system should only be a problem if fish stocking densities are low. Duckweed could in effect be used as part of ones ratio of fish weight/fish feed volume to plant volume.
2. I have found that duckweed in the main system causes problems with clogging. THe weed seems to drop roots all the time - like fine hairs - which then accumulate at the spot where the water comes out into the beds. Have others experiences this?

vb, ref (2) shouldn't be a prob with me as I was going to put the duckweed in the non pump tank and join the 2 tanks via a 40mm pipe siphon - but nice to know and watch for

The hairy root things end up in the water so will transfer between the 2 tanks Les.

oh well - back to the drawing board

I wouldn't be so quick to do that Les. When I had my problems I had a large amount of duck weed yet only a small grow-bed, running continuous flow and with a pretty crappy grid. See how it goes.

Les,

I will bring a bucket of Duckweed for you - I have heaps of the stuff at the moment, and yes VB it does drop a heap of roots, it has blocked the outlet on my super-dooper header tank so I discovered just a few minutes ago.
Wow VB, I will become a serial tester !!!!! pumping out stats .....thanks....
Muzza

The good thing about testing Muzz is that you don't have to do it all the time. Once you know your system is stable, you just do it every couple of weeks or when you notice that something isn't going as you would like it (eg fish stop feeding or plants stop growing). I haven't done a test for about 3 weeks. Might go and do one now :-)

Les, duckweed DOES NOT like fast moving or overly "choppy" water, so the sump might not see much growth.

Yep, testing good for setup until stable, then forget about it until your system looks smells (or tastes ) differnt to what you've been acustom to.

Steve

LOOKS LIKE STEVES BACK HOW DID THE HOLIDAY GO !Silly me just read the other linkes and realised he is at an internet cafe [not thinking straight]

Yep - intend having one tank as the sump/fish tank with the pump and growbed return and the other hooked up with a siphon so that there will be no/minimal turbulence (I hope )

Will put up some pics shortly on my thread to give a better idea of how its gonna work - right now I am in HSM jumping from one area to another as priorities change