notg2009 said:
Total hardness (as CaCO3) of my tap water is reported as 122. Magnesium not reported. pH ~7.6, Ammonia 0.25, nitrite 0, nitrate ~20. Water temp ~78 in my tank.
If I don't provide carbon as Excel, then do I have to have a homemade or commercial CO2 diffuser?
Thanks for all the great advice everyone.
There will be no issue with the GH (hard minerals), but it is one thing to always check. GH at 122 is presumably ppm (parts per million) or mg/l (milligrams per litre, essentially the same as ppm), which equates to around 7 dGH, ideal for the plants mentioned, and soft water fish too.
I'll explain about carbon now. The primary source of carbon for plants is CO2. Some plant species, namely those like
Vallisneria that occur in hard water habitats, can use bicarbonates as a source of carbon in addition to CO2. Some plants, such as mosses, cannot use bicarbonates at all. Most aquarium plants, including those you mentioned, will use CO2 primarily.
CO2 is more naturally present in an aquarium than you might think. The main source is the breakdown of organics by bacteria that occurs in the substrate. Respiration by plants and fish, and some bacteria, also produces CO2 but this will be less than what occurs from the organics. So don't be too thorough in cleaning the substrate. Other nutrients will be released from organics too, and taken up by plant roots, but the CO2 is the most important. This will usually be sufficient for the needs of the plants, provided the light and other nutrients are balanced accordingly.
Carbon is a macro-nutrient, but the amount required by a plant will be determined by the light intensity and duration as well as the other 16 nutrients being available. Photosynthesis will occur when everything is there, and as soon as something is no longer sufficient, photosynthesis slows and may cease altogether. At this point algae has the advantage. My point here is that the balance of light intensity and nutrients, plus light duration, is the key to good plant growth and no problem algae.
This brings us back to your present situation. A single T8 tube over this sized tank will provide low to moderate light (once you replace the present tube with one I mentioned previously). The needs of the plants for nutrients will thus be less than what it would if the light was more intense. It is fairly easy to add most nutrients via a comprehensive liquid supplement, and substrate tabs, but for CO2 we rely on that naturally-occurring. We refer to this as a low-tech or natural planted tank method. Adding CO2 by diffusion is only needed when the balance is raised, such as with more intense light and more of the other nutrients, and then we are moving to a high-tech method.
Last comment on light duration. Once we have found the balance between light and available nutrients, the duration factors in. CO2 is the one nutrient we are not adding, but relying on what is naturally occurring within the system. So in most cases, this is the factor that determines the duration. Once the CO2 is depleted, or has been reduced to below the needs of the plants, the continuing light plus fertilizers will encourage algae. I tend to suggest starting with around eight hours of tank lighting, once everything is balanced, and depending upon algae this can be increased or reduced. In my own fish room, with seven planted tanks, I have found that eight hours is about as long as the light can be on; one tank is reduced to seven, solely due to algae.
Byron.
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