I can not believe this conversation has been going on this long with nobody challenging it. I have been biting my tonge, but I can't take it any more!
Wow, much effort went into this I can see, but I disagree with so much of it. The term low light is so subjective and misleading when every other componant to successful plant keeping is not addressed. I think in a sense it is mis leading to simply make a blanket list of plants under the term "low light".
The definition of low light to most people new to the hobby is whatever light came with their aquarium, and then maybe bumping that up to between 1 and 2 watts of flourescent light per gallon of water. I don't think half the plants on your list would grow in those conditions, and even if they do survive, what kind of condition are they in?
The stem plants in particular I have a problem with. Generally speaking, stem plants are the most light demanding of all aquatic plants. There are a few exceptions. Most of the exceptions are now illegal in the USA because they grow so prolificaly. Rotalas, Stargrass, Ambulia? Are you serious?
Downoi? Low light? HC? Thats crazy! You are telling me HC is a low light plant? I would love to see that. Hygrophila difformis under weak light has thin stems that can not support the weight of its own leaves and flops over. With strong light and re planting tops the stems remain strong, thick and sturdy.
Any floating plant is pretty much a given. When it is two inches away from the light, any plant will grow. A couple of the plants on the floating list technicaly I would not call floaters. They are stem plants that will take root in the substrate under bright light.
Yes several common Cryptocoryne species are very tolerant of low light levels and growing submersed, but they grow painstakingly slow. Like an inch a year. They might as well be plastic. Balansae, retrospiralis, aponogetifolia, and pygmaea really do better under high light levels. Balansae in particular can be quite finicky.
Vallisneria I would defintly not call a low light plant. Not in a million years. Dwarf Sag.. yeah, you can get away with it, but the leaves will be much thinner than under high light. Micro Sword - Lilaeopsis braziliensis
, now I know you have never grown this plant under low light. I won't believe it for a second. This plant has always been know as being the MOST light hog of any foreground plant. It is the KING of high light plants. Unless you are growing it in only inches of water, there is no way it would survive.
Under weak light the plant will only survive on whatever energy is stored in the bulb, and most likely will only grow a few inches tall or have thin weak leaves. Once the energy in the tuber is used up, then the leaves die off and it will not grow back. Under good light, and good feeding, the plants grow to be huge, over two feet in length, tons of leaves and flower stalks. Aponogeton boivinianus is the most light finicky of all of them.
Sword plants. All sword plants more or less grow the same and are sort of iffy in the low light catagory. NEWBIES often think that the sword they bought potted that has been growing "well" in their ten gallon tank for the last 8 months is just wonderful. You and I know that a healthy sword plant would swallow a ten gallon tank for lunch.
Red Lotus - Nymphaea zenkeri 'red'
, If you want Tiger lotus to have leaves the size of a quarter and grow to be maybe six inches tall, then grow it under low light. If you want leaves the size of your hand and the plant to be the dominate focal point, give it some real light, C02, and feed it at the roots generously.
A true low light plant list is much shorter. Maybe ten plants.
I know there is a lot of discussion here about various conditions to make these plants grow.
It doesn' matter. All people are going to read is, OH this is on the low light plant list, so I can grow it in my 55 gallon tank with my 15 watt bulb.
Do you realize how hard it is to convince some fish people that if they want to grow plants the little 15 watt bulb on their 55 gallon tank just ain't gonna cut it? They will blame the plant, or the store they bought it from, or their water, or they will dump a gallon of fertilizer in the tank, anything except the light. They will finaly give up and go back to plastic plants. Having a list like this REALLY HELPS.
This is the most insane list of "low light" plants I have ever seen. You might as well say every plant is low light.
If you want to engage a conversation about how having 40 or 50 ppm of C02 and half a watt of light per gallon of water will enable these plants to grow fine, then OK. If you want to talk about a low tech, soil based tank, or the Walstad method, fine. Do that and open that up to debate, but don't call it a "low light plant list". Good grief.
Let me also add, I mean no dis respect to any one. I am NOT making a personal attack on any one here. I know James is very well meaning and a generous person who only wants to help. He enbodies the very spirit of what this forum is supposed to be, but I think this thread has serious flaws and can cause a serious problem. I believe it is extremely misleading, grossly generalized, and very open to interpretation.
So I planned on planting some mature swords in my 20 tall low tech, but instead I planted a 6 inch tall amazon and a 7 inch tall osiris. They have been chilling for a week now and don't seem to be struggling at all...Ill keep you posted in a few more weeks....btw, I dose 1.5 mL excel once a day or 2 and I dose a mL of FLuorish once a week after water change, thats it.
LOL.. You see! Thats exactly what I am talking about. A healthy sword plant would out grow a 20 gallon tank in less than six months. Just because it doesn't die in two weeks does not mean the plant is healthy. Sword plants are like Oscars. You can put a baby Oscar in a 20 gallon tank, but it is not a good idea. It does not stay a baby for very long
One other note: I know you posted this on at least three other forums, and your low light plant list is different on each WEB site. My comments on specific plants were from your list on aquaticplantcentral.com which I presume are also on your list here, but I did not compare plant by plant on your two lists. That was too much work!