Hello,
Yes, I have no doubt regarding your experience, and many people have similar experiences. Again, I did not say that one is guaranteed to have problems. What I said was that the probability of having issues is increased by not doing water changes. There are many things that contribute to success or failure and so not doing certain things can be counteracted by doing other things, and so forth. It's the combination of things that we do, not just any one thing. For people who DON'T have the experience, it is a better option to do all the things that contributes to success and to avoid doing all the things that contribute to failure.
Aquatic plants have a very thin cuticle. Aquatic leaves interface with the water column and with the rest of their environment by contact with roots and leaves. Many people assume that the direction of traffic is one way, that nutrients and CO2 only flow into the plant. This assumption is incorrect. When plants metabolize carbohydrates built from CO2 and nutrients, like us, their cells produce waste products, such as CO2 and carbohydrate residues. These waste products are dangerous and the plant expels them constantly in exactly the same way that we do. Plants also have a symbiotic relationship with certain microorganisms surrounding them. These germs require carbohydrates, and so some of the products that the plants expel are actually the same sugars that they produce as a result of photosynthesis.
Aquatic plants fed with CO2 enrichment therefore leach massive quantities of detritus out into the environment. This can be seen by shaking the plants and observing the cloud of "dust". Also, it can be seen by the level of dirt in the filter. These are all organic waste products. The detritus that coats the leaves acts to block nutrient and CO2 absorption. So plants can become suffocated by the level of waste. Does this always happen? No, because there are other factors, such as the lighting, the nutrient and CO2 levels, the flow and distribution and so forth.
Since these waste products are organic, they rot. When they rot, the production of ammonia results. The plants can reabsorb and recycle the ammonia, however, the microorganisms will oxidize the ammonia as we know from the Nitrogen cycle. The Nitrogen cycle requires Oxygen in order to oxidize these products, so that Oxygen is pulled from the water column. Again, is this always detrimental?, No, but in general, when new plants grown in emmersed conditions are flooded, the leaves are not efficient to begin with because they have been grown in air. The waxy cuticle is thicker and it is more difficult for these leaves to produce food and to make use of the light, CO2 and nutrients. So this is why, in many tank startup, failure occurs, because the hobbyists stacks the odds in favor of failure. They present too many obstacles for the plant to survive by adding too much light, by allowing the buildup of organic waste, by poor CO2 and poor flow distribution.
So we need to "peel the onion", so to speak, by undoing or removing as many obstacles as possible to allow the plant to breathe, to make food and to transition new leaves to a submersed environment. This increases the probability of success and minimizes the loss of tissue that we see so often.
Cheers,
