I wanted to find a way to ensure my phalaenopsis orchids always had enough water, without getting too much. By chance, I found out that they are actually very adaptable to hydroculture. Here are my findings, enjoy!
Step 1: Things You Will Need
1) An orchid in a see-through pot with holes in the bottom, I used the plastic pots they are bought in
2) An outer see-through pot with no holes in the bottom, I used a glass pot. The inner pot must fit inside the outer pot.
3) A shell or snailhouse or something else rich in calsium
4) At least two red ramshorn snails (Planorbarius corneus)
5) Some water, clean enough to use in an aquarium.
Step 2: Align the Pots
Find a way to arrange the pots so that the upper limits are aligned (at the same level). If you did not find a perfectly sized outer pot, then you might have to put something beneath the inner pot, to keep it from sinking down. I have used a medicine dosing cup.
After aligning the upper limits of the pots, there should be an empty volume between the pots that equals at least a glass of water, if not you must find a larger outer pot.
Step 3: Add Snails and Shell
Next, put a shell or a snailhouse inside the outer pot. It doesn't have to be more than a single, small shell. It should be untreated, a shell found on the beach is perfect. The ramshorn snails will use material from the shell to build their own shell.
Put between 2 and 4 ramshorn snails inside the outer pot, it is really important that you use a type that does not eat live plants. That means you cannot use giant ramshorn snails, which are in fact not ramshorn snails but a type of apple snails. I suggest red ramshorn snails, they work well and are very common in aquarium trade.
Step 4: Assemble and Add Water
Place the inner pot inside the outer pot. There should now be a free space under the inner pot, equals to at least a cup of water. Now, fill it up with water, just let the water pour though the potting mix of your orchid pot.
Fill up enough water so that it almost reach the bottom of the inner pot.
Step 5: Observe the Snails
Place the orchid in a window sill.
Within the next few days, check that your snails are alive and well. Ramshorn snails normally move around a lot. If they are not doing well, the best is to start over with new, cleaner water.
The snails should not be fed, they get enough food from cleaning the water from algae. They will adjust their numbers to the level of food available.
If all the snails die within a few days, you probably didn't use clean enough water, try again with rain or pond water. If all the snails die within a few months, you probably keep the orchid too dark. The snails feed on algae, which need light to grow. Phalaenopsis orchids are tough plants, so they can probably survive with less light than the snails. You can try to place a lamp nearby.
If all the snails die after more than six months, you might have a toxic build up of nutrient salts, especially if you use too much plant fertilizer. Try shifting the water every few months.
Step 6: Observe the Orchid Grow
Even if your orchid did not originally have roots growing out from under the pot, the humidity inside the outer pot will give it enough water, as long as the water surface is close enough to the inner pot, up to a few centimeters will do. This was actually my original plan: to have the orchids watered by the precipitation from a water surface. This works very well, but eventually, the plant will send roots through the holes and into the water.
These roots will continue growing deep into the water, and will thrive and grow even if permanently submerged into water. The ramshorn snails will keep the submerged roots clean and nice.
Step 7: Q & A
Q) Do the snails ever need feeding?
A) No. If you keep the orchid in sufficient light, the snails will have enough algae to eat. They will adjust their population numbers to the food available.
Q) Do you have to add new snails when the old snails die of age?
A) They normally lay enough eggs to keep the population stable, but if the water volume is very low, or their "aquarium" get too little light, it might be too harsh environment for them to reproduce, even if they live long enough to die of old age.
Q) Do the pot or the water smell?
A) No, the snails keep the water very clean. If the water is never shifted, and the outer pot is never cleaned, it can build up a layer of "snail poo" in the bottom. It will take a very long time, several months. This looks like green pelletized algae and does not smell at all in the pot, but it can smell a bit like "pond mud" when you pour it out. From time to time, a snail will die. This will not smell and the very tiny carcass will be eaten by the living snails. The shell will turn white but will last a long time if not removed.
Q) Will the snails eat healthy roots?
A) They do sometimes take small bites off new shoots, but they don't continue for some reason. It doesn't seem to affect the plant, and the roots continue growing like nothing happened.
Q) Will there be other critters?
A) Absolutely! There will be a complex ecosystem within and above the water. Some very tiny flying critters will be numerous just above the water, but they are so small that you have to look very close to see them. They will enter the lower, more humid part of the inner pot, but I have never seen them in the drier parts on the top.
Q) Do the water ever need changing?
A) I suppose, but it seems to tolerate just adding new water for a very long time, at least a couple of years. And I only use tap water (though Norwegian tap water is very clean). The snail poo sinks to the bottom and looks like very tiny algae pellets. These will be surprisingly stable, but new algae grows well on the surface of the pellets, so the snails prefer to graze in the bottom layer. In my experience, the layer will stabilize and not grow thicker than 5-10 mm.
Q) What happens when roots die?
A) Orchid roots die from time to time. If it is not more than a few at the same time, the snails will eat the rotting roots and there will be no problem. But my impression is that rotting roots are somewhat poisonous to live roots, and can cause other roots to die if they are close. Obviously, this can cause a chain reaction if there are many roots in a limited space. This is the case if they grow submerged in water, as well as if they grow densely in a pot. If this happens, the best is to repot the plant, either put it in a larger pot or remove much of the roots. Less dense root system makes a "rotting root chain reaction" much less likely. Personally, I have never bothered to repot, and have experienced a couple of rotting root chain reactions with little or no effect on the leaves and flowers. Snails multiply temporarily because of the nutrition boost of the rotting roots.
Q) What about fertilizer?
A) I use fertilizer regularly, in doses recommended for orchids. It doesn't seem to harm the snails or the roots or build up toxic levels in the water - I find it surprising but this is my experience.
Q) What are the main advantages with this watering method?
A) It is really easy to get good results, as the plant always has access to the exact amount of water it prefers (if there are roots growing into the water). Also, there is no need to water regularly, no problem going on a long vacation. It is easy to see that you need to add more water, because the water level is visible from outside. And of course the snails are kind of interesting to watch.
Q) Do the pots have to be see-through?
A) Yes, Phalaenopsis orchids really prefer to have their roots exposed to light. This seems to be even more important if the roots grow under water.
Q) How much water is needed?
A) Quite a lot actually. For every fully grown leaf, a Phalaenopsis orchid will consume approximately 1 L of water per year if grown indoor (there are many other variables too, of course). So even if it is perfectly doable, you will need a rather large outer pot in order to actually water a Phalaenopsis orchid only once a year.
Just a sidenote: in case you wonder why there are no aerial roots, it's because I cut them off for aesthetic reasons. I don't think they look nice. As long as I have healthy leaves and flowers, I don't see any reason why they must have aerial roots.