Most of the information on the web concerning planted tanks and aqua-scaping is focused on CO2 enrichment methods. However, the addition of CO2 is not the only way to achieve a beautiful planted aquarium. On top of that, a lot of the information on the internet concerning non-CO2 methods or so-called low tech planted tanks focuses on the use of various substrates (see: How to: Setting Up a ‘Dirted’ Tank) to encourage better plant growth. However, this article will focus on non-CO2 methods that emphasize the importance of water column dosing. Hopefully this article will demonstrate that planted tanks do not need to be complex in order to be beautiful.
Difference Between CO2 and Non-Co2 Methods
Given the goals that most people set out for their planted aquariums, it seems odd that more people don’t choose to use non-CO2 methods, as non-CO2 methods require less money, time and effort. CO2 and non-CO2 methods work for all the same reasons, but the plants in these systems grow at different rates. Plants in low tech planted tanks grow about 5-10 times slower than plants in CO2 enriched tanks.
Mechanics of Non-CO2 Methods
Due to the reduced growth rate in non-CO2 systems, it is often possible to eliminate nutrient dosing all together provided there is a nutrient rich substrate. The growth rate of plants in these systems is such that the fish waste alone is able to supply the nutrient requirements of the plants. This means that a balanced fish load and feeding routine is essential, since this is the main source of plant nutrients. As fish waste is a product of the food eaten by the fish, an understanding of fish food as a nutrient source is essential. While fish food varies in the amount and ratio of nutrients it contains, it should not be an issue unless certain nutrients become limiting.
In CO2 enriched systems, large amounts of nutrients are dosed and high lighting is used. This is all in proportion, as the growth rate of plants is only as fast as the most limiting input. Therefore, in non-CO2 systems, lower lighting can (and should) be used. 1.5 to 2watts per gallon is ideal. If higher lighting is used, CO2 becomes a limiting factor, which allows algae to grow better (algae need higher light to grow well in non-CO2 enriched systems whereas the plants are much more limited without CO2).
Poor Plant Growth Causes Algae
The causes of algae are a much debated topic. Many factors have been suggested, including; allelopathy, iron limitation and phosphate limitation. However, none of these are supported with conclusive evidence. By far, the best method of algae control is healthy plant growth. Healthy plant growth can be achieved by ensuring that nutrient levels do not become limiting.
The same applies for CO2 enriched systems. Algae is the indirect result of poor plant growth. Thus, plants define the system. When plants do poorly, they no longer define the system, and algae can grow.
CO2 limits plants much more than algae. However, over time, plants are able to adapt to low CO2 concentration by producing more RuBisCo and associated downstream enzymes to fix and utilise CO2 more efficiently. Both plants and algae are able to adapt to low CO2 environments and induce genes to make enzymes that concentrate CO2 around Rubisco, the CO2 fixing enzyme. Once the plants do adapt to low CO2 levels, they can do well. Stability is the key in any planted tank and as long as the CO2 is stable, the system will function well.
When the CO2 concentration is increased, this causes the plants and algae to destroy the mechanisms that allowed them to fix CO2 more efficiently (enzymes). Why keep all this machinery around if you no longer need it? Doing weekly water changes increases CO2 levels and effectively “fools” by making them “believe” that there is more CO2 present than there actually is. This in turn helps encourage algal growth. While ‘High-tech’ systems tend to employ large water changes, this does not work in non-CO2 systems. Large water changes cause spikes in CO2, creating instability.
Low tech planted tanks have the same plants as those in CO2 enriched systems, therefore, as we know the rates of uptake, we can simply scale down the rates for the non-CO2 dosing routine.
When there is a heavy focus on water column dosing, it is important to look at dosing from a management perspective. While there is a method to add just water column fertilizers to the inert sands, adding nutrient rich substrates will enhance the overall stability of the system in the long term. On the other hand, by using the water column alone, we can measure the levels of each individual nutrient easily.
The addition of CO2 is not the only way to achieve a beautiful planted tank. Moreover, the use of nutrient rich substrates, while beneficial, is not essential in non-CO2 systems. Water column dosing alone can achieve beautiful results. Water column doing is often overlooked as not being enough to achieve decent plant growth, however, this is not true. Water column dosing allows the hobbyist to be more precise about the amount of nutrients added to the system and therefore, the overall stability of the tank can also be monitored with ease.