It is my understanding that organic fertilizers need soil in order to break down and be utilized by the plant. But most orchids are not grown in soil, and organics merely accumulate in the medium and begin to burn the roots. If you do use organics, what medium do you grow in?

Its not an issue of no soil but a lack of beneficial bacteria and fungus. Most mediums will have these if the conditions are right.

Most organic fertilizers are soluble and non-soluble. The soluble can be use right away by the plant and the non soluble needs to be broken down via fungi, enzymes, ect.

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9 times out of 10 there not beneficial! I find it important to add trichodrema to help protect the plants from attacks. Fungi which do most of the eating of organics really only like moist woody mixes.

Fish meal and blood meal produce ammonia as they decay. Potash is a salt of potassium.

Nutrients-- all of them, regardless of their source-- ARE chemicals, by definition.

Many of those chemicals are, technically speaking, organic, and many are salts. No way around that. The term "organic" as it has been applied to agricultural styles is a really awkward, confusing usage of the word. If you're going to talk about the specifics of fertilizing, a more specific vocabulary helps. Organic vs inorganic is a different use of the word than organic vs artifical, and so on. Hell, when you get right down to the nitty gritty even scientists argue about what's organic and what isn't, and does carbon dioxide count, etc.

So, when you say "organic" are you trying to refer to compounds that contain carbon, or are you actually talking about compost, or humus, or are you referring to something natural vs something artificial, or something solid vs liquid, or...?

"Organic" is not quite the issue. The question is bioavailability, or whether the nutrients in the fertilizer exist in a form that is directly available to the plants or not. If the nutrients are contained in compost-- chunks of decaying stuff-- then yes, they need to be broken down further before plants can utilize them. It's not so much that soil is needed for this to happen, as soil/humus tends to be the result. Along the way, the active decay of unfinished compost or the pileup of material can hurt roots, by different mechanisms of damage than that caused by accumulated salts.

Epiphytic orchids in the wild get most of their nutrients from stuff carried in the water that flows over them, and can't tolerate a constant rot-happy cover of soil/humus. This means we generally need fertilizer that's already pretty thoroughly broken down for them.

I use live fish and aquatic compost (tea, I suppose?), myself, with some added micronutrients.

Folks:
this is one of my favorite topics. In summer when the orchids are outside, I make up a batch of witch's brew for them. The ingredients are chicken manure (from my chickens - high in ammonia), seaweed and/or fish fertilizer, a little epsom salts, and whaterver else is on hand that looks "delicious."
Bat guano, yes for the ceologyne, brush up from barn floor and just toss some on the plant.
This is only for the summer diet when dunking and hosing are possible. People really admire my plants, and when I mentioned this ritual at a club meeting, the president said, "Stop scaring the beginner!" ha ha ha ha hah ; -) Works for me.
Cheers~
ML in WMass

Goldfish pond water is a great fertilizer. I miss my ornamental pond everytime I water the plants (but I don't miss all the work I put into it!). The fertilizer for the lotus were probably a good addition to what the goldfish and decaying plant-matter provided. :)

Has anyone checked the dissolved salt content in fish pond water on a DSL meter?

Good point, I would think that the dissolved solids might get rather high. With pond water you are starting with tap water and then adding more tap water to make up for evaporation. Lots of other variables too. I much prefer to start with RO purified water and add defined amounts of chemicals.

There's a multitude of ways to test aquarium/pond water. Fish are much more complex, sensitive organisms than plants, and good water chemistry is crucial to keeping them healthy. Bad water will kill fish quite a bit faster than it kills plants.

We can test everything from pH to TDS and ORP, general hardness, carbonate hardness, ammonia, nitrite, nitrate, phosphate, copper, iron, dissolved oxygen, carbon dioxide, chlorine, etc etc. Unfortunately other things are not easy to test for-- potassium for instance, and most micronutrients.

There's a huge amount of information available if you look up planted tanks, aquascaping, aquaponics, and so on. The water that will keep aquatic plants happy can feed lots of other plants too!

When you see how the lilies and lotus thrive in a pond (especially a lotus with those lovely, fragrant blooms and five foot high leaves) you realize how good that water must be. :)