Hey, Gary. I am afraid I don't have a clue about the fertilizer except to begin it with very weak solutions. If you know what nutrients the epiphytes use, can you do a water composition test like what they do for drinking water? How do they do it for Hydroponics?
What I really want to do is pick your brain. I remember you mentioning the wall either last year or the year before that and then you didn't mention it again. Is it an example of what is being called a wall garden? I have been looking for info on that for the last couple of months and I think you must be the local expert now. I love hearing about your different projects. I just wish I had some of your weather. Can you recommend a source or two? I haven't heard the term seep wall before. Is that your name or is it an established term? What materials did you use? What kind of plants are appropriate? Did you use pockets in the wall? What is the source of the water and how do you collect any excess? Our Extention agent wants me to build one in the Master Gardener's Display Gardens. Maybe you remember me talking about my greenroof project. It has been finished for two years now and it is lovely. Sandy

Any pond place or even pet stores have nitrate, phosphorus, and nitrite testers you can buy.

Sandy
This "wall" is a bit hard to describe . It has several main functions but the primary purpose was to provide vertical grow space for various types of epiphytes. It is also a heating,cooling ,as well as a self watering
self feeding (maybe??) system. lol I'll just describe the layout method of only the "wall" because it takes a book to describe the whole thing.lol
It is located on the north side of the shadehouse wall,attached to the house wall, made mostly of 'painted expanding foam. It is above and behind the 150 aquarium. It has various "pockets" as well as natural materials for holdfasts for various types of plants. It is made and painted to look like a "rock " wall. It is 7x10 feet at this point. Water is forced by a pump from the aquarium
to the 5 foot level of the wall at a very low flow rate so it drips accross 7 feet of the wall. i call this a "seep" because it's too slow to be called a waterfall ??lol
The water flows down the wall and collects in a 2x6 foot "marsh garden" from there it flows into the lily pool
which is located outside the shadehouse in the yard. After being filtered it is returned to the aquarium.
The main purpose of all this was to expand the various types of grow areas and integrate the systems into a single system. Go from full sun to full shade, submerged to very dry. The goal is to make a "rainforest" rather than a collection of hanging pots in a grow area. Provide a home for the fish, lizards, frogs and birds .
Pix have not turned out well for several reasons besides the fact that I don't have a camera lol. None of the construction pix turned out at all and now the wall can't even be seen due to the plant growth. lol. 3 feet is as far as you can get from the aquarium due to terrestrial growth so can't even get all the tank in one pic.lol There is also shading , and reflections from the glass. i look at my pix and I get confused as to what it is lol. I can see that
the whole area is WAAAYYY to small and I'm hoping to expand to 25x25 feet and gain some roof height at least a couple of feet.
Hoovb Don't need to test to know that all these chemicals are present due to the fact the water is coming from cycled pond water. The question is what is too much ??
The water and marsh plants are no problem as you can't OD them but Epiphytes is a whole different story.
So far have not added any fertilizer to the wall part but feel almost certain that it's too weak particularly with "trace" minerals". But maybe not a problem??? thanks gary

My guess is, without testing the water the first indication of problems would be having the plants turn yellow. If you have plants in the pond that are doing well you probably won't have that problem unless your epiphytes have nutrition needs drastically different than the pond plants. I don't know what plants you have so I can't advise or research. I seem to recall they do have some different requirements. My plants would be totally different due to the climate.
I hate to think of the number of cans of foam you had to use. You must have molded the sections somehow. What did you use? Did you use some sort of backing? Did you mold it in sections? I would think that plywood would be too prone to rot but Styrofoam wouldn't have the structural stability without some sort of framework. The foam would make nice planting pockets too.
Is that 25x25 a typo? At 25 feet tall it sounds like you would have wa-a-ay many bearing problems. I would like to hear about some of the details if you have the time.
I guess your marsh would be something like a bog here. What are you using as a water distributor. PVC would be one choice but greenhouse drippers and emitters would certainly work and if they clogged they could be replaced without tearing the whole thing apart. They are a lot more flexable, too. The water would have to be filtered pretty well. Why did you not start it from the very top? It seems to me one of our forum regulars has a similar wall. She is in Florida too and gardens in an enormous greenhouse. Her name escapes me at the moment but her photos have been inspiring. She talked about the wall but I don't remember seeing any pictures. I'll look again when I have time. Thanks, Sandy

The only thing I can think of is that epiphytes might prefer slightly acid water - I'm thinking of the typical rain water. Whereas pond water tends to be somewhat alkaline, reasonably buffered around a pH of 8.3. I almost wiped out 700 or so seedlings one year using pond water because of that "little error"... they did NOT like water at that pH! Just a thought.
---David

Gary, I got the name, but I misspelled yours in the post I sent her. She has a current post on this page. It is Bihai and the post is Bloomers in the greenhouse unless my memory is messed up again. Her wall is a drip wall and is under construction. Sandy

Sandy
Bihai's GH is larger than my whole lot!! lot Mine was originally a 12x25 attached screen room.. Started using it for plants and have been modifying it ever since. It has turned into a jungle several times so in 2000 i started trying to integrate the various areas.. The original purpose was to "downsize" but find the water gardens and epiphytes my main interest. Have not really been expanding just rearranging . The "wall " was the offshoot of building a large terrarium decided to use the climate rather than artificial methods. Wasn't sure that I could keep an aquarium in sunlight or that i could keep the temps stable enough for the epiphytes. I was originally going to build a waterfall but resented losing so much grow space ,so went with both. have now made it through two winters and very encouraged by the results. So my goal now is to expand the SH to 25x25 with a 13 foot ceiling but city ordinance will only allow 9 feet.
have so far used 8 cans of foam. Sheet styrofoam was applied to the CBS walls of the house covered this with fiberglass tarp to waterproof, PVC pipes were put on the wall and covered with the foam. I didn;t go all the way to the top to keep the pressure down and to provide a very dry area for epiphytes. Part of the wall is under the house eaves so is even more complicated from light and lack of natural rainfall. So went dry there. Have been adding sections at a time gluing them in place with silicone and using various plants that I already have.
David The lily pool was originally a way to collect rainwater for the epi's but couldn't resist putting fish and plants in it lol.. So the water is generally from 6.5 to 7 O ammonia and nitrite and about 30 PPM nitrate. So is actually a good water source but if I fetilize the epi's obviously excess will drain into the water areas.
i recently had to redo the lily pool so it is isolated from the other water systems until it stabilizes. I didn't have a 1000 gallons of rainwater lol.
gary