Hi Roland,
Yes, the low cost is really the main point of the scheme, and that's why I point that out in the first paragraph of the post. Why pay for water when you have rivers of it falling from the sky every day?
But I also want to change people's concept of just what it means to provide a healthy environment for the fish. As many people do, beginners and experienced folks alike, in your mind you have the cart before the horse. The ecological system your fish live in is fundamentally structured around the plants, not the reverse. The two imperatives therefore go hand in hand. When you create an environment that satisfies the requirement of the plants, they then produce the environmental changes than benefit the fish. Plants do not simply sit there looking pretty. Plants are are chemical warhorses and they actively change the environment to suit their needs. Did you realize that all the Oxygen that is in the atmosphere right now came only from plants? Oxygen did not simply appear on Earth. Prior to the appearance of plants there was only CO2, Nitrogen and other noxious gasses in the atmosphere. Bacteria and later, algae, were the first to exploit the CO2 and water to make food. During this process they expelled Oxygen. It took a few billion years but we finally have an atmosphere that is 21% Oxygen. We could not have evolved into what we are today without this basic food making procedure of algae and plants. If plants disappear from the planet in significant quantities, our destruction will be assured.
In your tank, plants reproduce this basic and important process. They remove noxious Nitrogenous compounds and other inorganic toxicants such as metals from the water and they replace the toxicants with Oxygen, more Oxygen than the fish are able to obtain by themselves from it dissolving in the water from the air. Plants also remove and use the same Calcium and Magnesium that gives the water it's hardness. In so doing, plants also provide the extra Oxygen and carbohydrates necessary for the nitrifying bacteria to thrive in the sediment and in the filter, so you have a better, more diverse and healthier aerobic bacterial population in the tank and they oxidize the pollutants like Ammonia and Nitrite in the tank. The fact that your fish survived being thrown in the tank too early was aided in no small part to the beneficial action of the plants, who not only removed Ammonia directly, but also pumped up and accelerated the beneficial bacteria much faster than possible than in a tank devoid of plants. The only thing the plants cannot do is to remove the huge amount of organic waste that they themselves produce. You must do that with water changes.
So when you think about the tank system, it's better to think in terms of supplying the environment most beneficial to the plant health first. When you take care of the plants, they will then automatically take care of the fish. Obviously, we have to intervene because we have to set limits on the amount of CO2, and because it's a closed system, with no escape path for organic waste buildup, there has to be fresh new water regularly input to the system. The nutrients that we add do not harm the fish but under the lighting levels we impose, and under the CO2 levels that we inject, the nutrients are vital to the health of the plants. That's why, when we observe the tank and when we see problems with a plant, it is an early warning sign that the environmental conditions could be on the decline. So we try to find the best way to improve the conditions so that the plants are contributing to the improvement of the conditions instead of contributing to it's decline.
Hope this makes sense. 😉
Cheers,
