Paulo,
Do you really think that Tropica does not grow their own plants in an aquarium? Do you think they have difficulty?
You and others have difficulties because you roam The Matrix looking for answers that you like to hear instead of dealing with the answers that are difficult to achieve. As I explained ad nauseum, CO2 concentration levels are highest at the top of the tank, even if the light intensity is also at it's highest. If any pieces of the plant are sticking out of the water then that leaf has access to 300ppm of CO2. When you submerge the plant the situation changes and the conditions now depend on the gas concentration level as well as the flow and distribution at the location that it is planted. It no longer has a snorkel. The concentration of CO2 in a tank is never static and is NOT homogeneous. It can be 10X lower at the bottom of the tank than at the top. That's why flow/distribution, injection rate, light intensity and gas timing are so important. I thought you would have learned that lesson by now.
You have fish in the tank, so there is a limitation to how much you can push the gas to serve the needs of this particular plant at this particular time. Some time later the requirements will change because the plant would have adapted.
So the answer to your question is "It's not your water, it's your fish." get rid of them and all of these mysterious maladies will disappear and you will understand the truth, because you will be able to drive the gas to maximum levels.
I have already shown you the path for solving the other CO2 issues in your tank. You should ALWAYS suspect that the limitation of your plants is a CO2 limitation. Whether or not you can actually solve that problem is not a certainty. Of course you will not just throw your fish out the window. That's OK, but likewise, there is no need to waste energy looking under every rock for an alternate reason. If you have a CO2 limitation in your tank and if a particular plant does not accept your limitation then that's just life. Why should the fact that one plant is satisfied automatically mean that another plant will be satisfied?
It isn't your tank, or your water, or your spectrum any more than whether it's the day of the week or the phase of the moon. The explanation is very simple. One day, try a tank without fish - without limitations, and you will see how fruitless it is to blame all these various parameters. This is a carbon planet. Everything revolves around carbon. It's in your blood. All your cells feed using sugar, a carbon construct. When you lose access to carbon, you waste away. The same for plants and every living thing on the planet.
I don't have trouble growing plants because I always think my CO2 is never good enough. The people who have the most trouble are those who assume their CO2 is good enough. Only rarely is the cause some other factor, such as toxicity or parameters, but you must first exhaust every possibility of a CO2 shortfall first, not last, otherwise you will waste a lot of money buying replacement plants.
Here, look at this, a couple different species of ludwigia on the left. Amazing, right? Well, no, they are under duress from the lighting and as a result, are suffering CO2 deficiency. How can you tell? Look at the leaves. They are highly pigmented to protect themselves from the light energy and, most importantly, they are warped and crinkled. This is a classic symptom of poor CO2, but at that time I had similar limitations as you do now. There were fish in the tank and the amount of CO2 injection under
that lighting condition, required to solve this problem would annihilate the fish within minutes, so I had to live with it.
Here is how straight the leaves look when they are NOT under light/CO2 distress:
In your case, most likely it would have been better to exercise patience, to reduce the lighting and float the plants a bit longer. CO2 is NOT a pill that you take, or a button that you press. It's a very complicated excercise, and you have to accept that you will always be tweaking to get the best out of it.
You're not the first to discard the notion of CO2 shortfall. Have a look at this journal thread which goes on and on for 2 years. It took Tyropagus 2 Years to solve his problem.
http://ukaps.org/forum/threads/swamp-creek-2-years-on-updated-june-2012.11074/
Whether you accept that explanation, well, I leave the choice to you.
Cheers,
)the only way to solve the problem is to up the CO2 levels beyond what the fish can tolerate then you have two choices:
