Firstly, VERY nicely build!

Algae in the pond? Don't you have a filter system with UV? My pond water is crystal clear.

A few questions I like to ask as a pond owner....:

For the tube system, do you have constant water flow, or you put water in in intervals?

Do you guide the water back to the pond after the plant system?

How are the tomatoes doing? I thought they are VERY hungry and usually need lots of fertilizer?

I am thinking of a vertical tube and then feed the water back just in front of the filter system.

Thanks for the comments ... I don't use UV, when I started the pond I was cheap and simply scaled up what I used in my various aquariums. I have always found that enough higher plants will use and lock away the nutrients that the algae are after. It really would be just a couple weeks in the spring when the air/water temps were too cold for the tropical plants that the string algae would show up, and as soon as the plants got established the algae would go away.

What isn't pictured is the main filter, it is a 35 gallon barrel configured as what used to be called a "reef filter" it is fed by its own 900 gph pump.

The water is flowing constantly through the PVC pipe at a rate of about 80 gph, the plants in the boxes are receiving about 4 gph each. After it passes the plants the water returns to the pond via a small waterfall mixed with the water from the filter.

The tomatoes are indeed quite hungry as are the peppers, it was one of the reasons I chose them, my theory was that they would more quickly give me an indication of any nutrient deficiencies. (partly because the Hot Pepper Forum here is so informative). I am already adding small amounts of Iron, Magnesium and Potassium since they are not really provided by the fish waste, I would have been doing that for the aquatic plants anyway though... some time in mid July.

The Tomatoes and Peppers are both rapidly outpacing the plants I put in the ground for comparison. Some of the tomatoes are flowering already and the peppers are setting fruit. But the amount I am feeding my fish just keeps going up..with still no results from the test kit. (it does show results from a friends pond however so I know it is working)

Mhm, you let the water flow 24/7, don't the plants get 'wet feet'? (Actually a silly questions as there is also deep water culture).

For the algae, my pond has direct sun and there are no plant in it. This said (and I do lack aquatic experience), do you think the UV is counter productive?

And one more question, are your plants in a covered area? I mean, do they get rain?

My plan is a tower (like those strawberry towers), put Hydroton as a medium, and then grow hopefully some Chinese stuff, Choy Sum, Bak Choi.

For tomatoes and basil (and soon more I plan) I do fogponics. I want to have a box in my bedroom and the fogger is really noise free.

blattlaus, the PVC pipe system is really pretty much a standard NFT. Between each of the pipes is a small venturi to help re-oxygenate the water. I was concerned about the plants in the boxes but they seem to be doing fine.

As far as your pond is concerned I would think that if you have no plants the UV is pretty much a necessity. The UV should keep the water clear but the nutrients are still going to be present, unless you find some way to use them up you will probably be making a lot of water changes.

The plants get rain which isn't a problem, wind which is an issue for some of the plants in 2 inch pots, but the biggest issue I've had lately has been too much sun. These plants were all started under lights in the basement and I wasn't able to harden them off like I would if they were grown in dirt, as a result I'm getting a little leaf burn.

There are lots of videos on youtube with towers like you describe, there are even a couple versions sold commercially.. best of luck with whatever you decide to go with.

don't the plants get 'wet feet'?

The real problem with "wet feet" is a lack of oxygen. Roots need oxygen just as much as they need water and nutrients. Those plants that can handle living in stagnant mud are those that have low oxygen requirements. Flowing, recirculating water has plenty of oxygen mixed in, and that is what makes hydroponics possible. Oxygen requirement is also why plant roots tend to be in the top 12" of soil, even for large trees. Because the farther down in the soil you go, the less air there is. It's also why fluffy soil is easier for plants to establish in than heavy dense clay.

I had to look up what a 'venturi' is.... nice!

I am still in an early stage. The fish are there for ages, more because of the previous house owner.

Anyway, I think I will go the deep water 'Kratky' type with the difference that I will let the water constantly flow to the box. And I add an air stone too (since I have a unused airpump).

BTW, I never ever changed the water in the pond. In my area I get plenty of rain and quite often the pond overflows. The pond's Ph is 8.2 (despite LOTS of recent rain with a Ph of 5.0) and the TDS is 77. Can the plants handle the high Ph?

You will find that your pH changes throughout the day, with the lowest pH just around dawn and the highest late in the afternoon. Most plants can handle the normal pH range, it is only when the changes become excessive that there is an issue, Typically though I would expect to see unhappy fish before unhappy plants.