Backyard Aquaponics
A place to discuss aquaponics

Posting on behalf of a friend. He lives outside of Seattle Washington. He tries to grow watercress in a pot (see pic) semi submerged in an outdoor pond with great water circulation. Sun in the afternoon, only a few feeder gold fishes. watercress not growing at all after months. Didn't die but no growth. How come?


Sent from my iPhone using Tapatalk

Is he giving it any other nutrients, other than what the few goldfish provide?

Quite sure no other nutrients, is watercress a heavy feeder? It's not dying but also no growth at all for something that's supposed to be weed.


Sent from my iPhone using Tapatalk

I'm not sure of it's feeding requirements but I'm just thinking that if it's not growing it's probably not getting everything it needs, even though it looks healthy. I've grown upland cress in AP grow beds but never watercress. If your friend has some nitrate fertilizer or some blood and bone meal and is willing to add just a bit to the tray that might help it get going.

Judging by the number of leaves, I think the water lily might be able to do better also but it could just be the variety. Water lilies are heavy feeders so it might be sucking up most of the nutrients.

I think one of the problems could be that the pond isn't deep may be 2 ft? Current very strong, the pump used 2" pipe. It's outdoor and unprotected so difficult for fishes to survive in the environment not to be predated upon.

Watercress are supposed be weed for growing too fast, not here.


Sent from my iPhone using Tapatalk

I grow mine in a 100L media filled tub with clay balls but not fully submerged like he has.
I don't feel they need a lot of nutrients - I only run a few goldfish in that tank of mine and don't add anything else.

However my watercress variety (from seed packet) is more like a coriander sized leaf etc.
We tend to eat it more as a small plant (from seedling sized onwards).
Few seeds sprinkled in and off it goes - same for rocket.

Don't have any pictures at present and only have a small amount in tub
(just pulled a heap of watercress out to plant rocket as it begins warming up here and sun gets down side of my house again)

A couple of things occurred to me -

If this is the same watercress that Darren grows and the leaves are smaller than his, then maybe there is some stunting going on due to a lack of phosphorus. That might also account for the color in the water lily leaves although many varieties have this coloration so it's not a sure thing. Find out if you friend is using flake goldfish food. Usually this type of food is made to maintain goldfish not help them grow so nutrients are lacking. The suggestion I made earlier about blood and bone will probably help with this. Switching to a good quality commercial pellet food would also help.

I notice that there is almost no algae in the pond - usually there will be a fair amount of algae if there is much available phosphorus.

I don't think friend is feeding his gold fishes so they are growing much either


Sent from my iPhone using Tapatalk

Try moving the tray onto the water fall area,I used water cress as part of the filtration in MT Koi pond to help with nitrate levels,I had a channel where a small amount of flow was past through,it grew very well like this,sitting it in the moving water will ensure that what ever nutrients are in the water as passing the root system. Trim it back get al the dead stuff out so it has chance to restablish itself, Scotty though it might be low Phosphorus,looking at the leaves i don't think it is,I think Nitrogen is going to be lacking,but a simple test would show this.

If it's nitrogen deficient then it's not a very bad shortage of nitrogen or the leaves would be lighter than they are (I only see a few yellow leaves). Moving the watercress sounds like a good idea - more oxygen and possibly gets some additional nutrients. Doesn't sound like much feeding is going on so we may both be right.

I still reckon that you try lifting the tub partly out of the water. So the surface media is damp but not under water. The variety I grow thrives in a normal media bed with water level 7cm (3") below surface.

+1dasboot. Watercress groes well in flowing water, while the pond may have great circulation the plastic ppt doesnt look like it does. When the nutes get flowin the cress gets growin!

Heres whats left of my water cress (at back of tub). I have been harvesting at half a 100L tub every couple weeks over winter - it is pretty low-care and direct from packet seeds.

Front is now rocket. As is couple of other smaller 100L tubs I have hooked up together.

I don't believe nutrients are his issue - it is water circulation and movement of fresh water through the root zone.
Hence lifting the tub and making options ti make sure water is flowing through the media will help a lot.
At present it is probably anaerobic in the tub.
Just lifting the tub out of the water and feeding it with a gravity feed from the top pond and some drain holes in the tub and he would get heaps more growth.

as per previous post the variety I grow looks a bit like coriander, and is mostly harvested and eaten whole as 4-8" plants. Have quite a peppery-mustard taste.

They require very little nutrients... why I grow them over winter as a filler while the system is slow.

Sounds to me like a combination of what's been said above. Nutrients plus moving water which gives better oxygen. Try it and let us know.

Dif

your cress looks like my coriander what variety is it as its end of summer here and I'd like to get some packets of winter plant seeds ready. Thanks. KE

Darren that is certainely how it should look...