Back in the mid to late 1990's I heard from an old friend of mine in Virginia (USA) that he was going to sell his house and retire. He had a small pond in his property in which he had the Japanese (both Kyoto and Tokyo mixed) strains of Aldrovanda growing, and was going to be drained and destroyed by the new owners.
I went out to canvass about 20 prospective sites, within a day's driving distance from my house, which were isolated, away from any pristine natural water ways and protected forests, and sought out privately owned sites, and got permission from their owners to attempt to grow Aldrovanda in them; some were old abandoned sand and gravel pits and quarries, fishing holes and artificial ponds, a few had a presence of sphagnum and even some D. rotundifolia and a few Urics.
I took about 2 years scoping out prospective ponds and sites, as I have given up trying to grow them in containers. Good thing my friend had some delays in selling his house!
There was a small and shallow pond in back of a shopping mall near my house, where I had attempted to naturalize a few Utrics and Drosera, but they all failed to thrive and died.
It was also loaded with clouds of algae blooms, and the surface choked with duckweed and a small leaf water lily that grew so thick that it completely covered the surface to the point where I couldn't even see the water, mice and rats would run across them without even getting wet. This site had already been cleared for development, and further excavated to be used as a rainwater discharge basin for the local roads and community, and eventually this shopping mall. Some local wetland plants came back, but also several nonindigenous plants invaded the area as well. It is an ecological and conservationists wasteland and a botanical junkyard. Massive algae blooms occurred constantly.
Yet, there were large hummocks of Juncus, Carex, Typha and Pragmites scattered all over this shallow pond, including a few Isoetes, and looked very much like the natural sites of Aldrovanda found in Europe. Still, I referred to this site as a "disgusting mosquito infested, slimy algae scum puddle", as it would also dry out completely at least once or twice every summer to the point where I could walk in there with my shoes, (even in the deeper areas), without getting wet. I had tried several time to get several local Utric's to grow here, but they got swallowed up by those massive algae blooms, failed to thrive and never returned after winter.
In 1999, I brought back several thousand strands that I raked out of my friend's pond in Va., the day before. I stopped by the mall to pick up a few things, and just before I headed out to those other sites, figured I might have another look at this pond behind the mall, and grabbed a handful of Aldrovanda and threw them into the Phragmites section, and kissed them good-by, never expecting to see them alive again.
I stopped in there several months later, just before winter set in, and noticed that they had grown that sumer, but were barely visible as they were completely consumed in massive clouds of filamentous algae blooms, but again, didn't really expect them to survive here anyway, and wrote them off as another lost cause with the winter soon approaching, and the pond is so shallow, that it freezes solid every winter.
The following Spring season, 2000, I went around to all of the sites where I attempted to naturalize them, but found nothing. The shopping mall was undergoing some major construction, and heavy equipment blocked my access to this pond, but I didn't expect to see any Aldrovanda there anyway, just like the attempts I made with Utrics in earlier years.
I continued to search all the other sites (where I seriously hoped and tried to naturalize them) for signs of hope and reemergence of Aldrovanda after the winter season, but they all failed. Now, I realize that those other sites were too deep, too cold, too dark, too acid, too clean, and had the wrong plant associates growing.
In late April 2001, construction at the local mall had been completed, so I took walk around the periphery of the pond, and was completely astonished to find a four inch strand of Aldrovanda floating near the Phragmites, where I had thrown them two years earlier! ;D
I went back to the mall, to the Sporting Goods store, and purchased chest waders, and walked into the pond, and looked at the base of a Juncus hummock and saw something like this:
I spent several weekends removing these nasty small leaf water lilies, and duckweed, so that the Aldrovanda would get some sunlight, otherwise either of these would out compete the Aldrovanda for sunlight, and drive it to oblivion. The water lily reproduces vegetatively by stolons, like strawberries, sending out dozens of runners, with new plants, that also send out runners, forming thick mats, they also produce tubors from their roots, which breaks off, drifts into remote areas and produces hundreds of plants that seize and overwhelm the surface in just a few weeks.
This site has a conspicuous presence of clay, and the water tests neutral (pH=7.0) and is moderately hard. The Aldrovanda grows in the shallow mud and loose slurry of detritus and leaf litter of those monocot plants where the CO2 levels and the population density of the zooplaktonic community are the highest, less than a foot deep, (ankle deep).
It was the LAST place I ever expected to see them alive again, but turns out this is the only place where they naturalized! Again, they ONLY grow in VERY shallow water, ankle deep to knee deep, no more deeper than that!
There are areas that suddenly drop to waist deep, within just a few feet, but Aldrovanda refuses to grow in those areas, and quickly go into decline if they drift into those deeper areas, despite the fact that the water chemistry, sunlight exposure and temp are exactly the same! The ONLY difference is the population density of the zooplankton community, and the close proximity to those moncot roots which drops precipitously after 12 inches depth, which proves that it's NOT the chemistry of the water, but it's the Biology of the water that is the key!
They are integral members of a complex symbiotic community, and cannot live well without ALL it's constituent members present in close proximity within an intimate relationship with all the other members in this niche.
They also have a strong need for CO2 which is constantly released by the roots of monocot plants and the zooplanktonic community by respiration, but also do best in very dirty, and disturbed water where the detritus, silt and clay are churned up which releases the minerals and those small creatures that live in the silt and detritus layers; this also causes the water to warm up more, as it absorbs more solar energy, which causes the rate of respiration increase, and produces more CO2.
Also, notice a complete lack of any algae! In fact, algae goes into decline in the presence of a healthy Aldrovanda patch, and when I see a dense cloud of filamentous algae drifting in the pond, I scoop it out and toss it into a dense patch of Aldrovanda, and the algae completely disintegrates and disappears in two days!
Copepods and small snails graze on the Aldrovanda strands grooming off any algae, and keep it clean. Small snails also pull out the spent carcasses from the old traps before they get loaded with algae, and both often wind up as food for the Aldrovanda as well.
Curiously, there have NOT been any more of these catastrophic cycles of algae blooms and crashes since the Aldrovanda has established itself in this pond! - And, the Utrics also have flourished, but occupy deeper waters, and do not compete with the Aldrovanda.
Here are a few more pics:
After a dry spell, the pond nearly dried out again, but a rain storm that lasted all week, flooded the pond. There was an area where some grasses grew up from the mud, and some Aldrovanda found themselves growing with them, but now, the grasses were well under water, and the Aldrovanda rose floating to the surface. After I took this, I noticed a young pickerel looking back up at me!
Here they are growing in-between Carex hummocks, in only a few inches of water.
Hope you enjoy!