Why pH is so Important for Aquarium Plant Growth
When the pH is not at the proper level the plant will lose it's ability to absorb some of the essential elements required for healthy growth. For all plants there is a particular pH level that will produce optimum results (see chart 1 below). This pH level will vary from plant to plant, but in general most plants prefer a slightly acid growing environment (between 6.0 - 6.5), although most plants can still survive in an environment with a pH of between 5.0 and 7.5.
When pH raises above 6.5 some of the nutrients and micro-nutrients begin to precipitate out of solution and can stick to the walls of the aquarium. For example: Iron will be about half precipitated at the pH level of 7.3 and at about 8.0 there is virtually no iron left in solution at all. In order for your plants to use the nutrients they must be dissolved in the solution. Once the nutrients have precipitated out of solution your plants can no longer absorb them and will suffer (or die). Some nutrients will precipitate out of solution when the pH drops also. The chart below will give you an idea of what happens to availability some of the nutrients at different pH levels:
We have found that the addition of PMDD nutrients assists in the lowering of pH. Always add nutrients to the water before checking and adjusting the pH of your water column. The fertilizer will usually lower the pH of the water due to it's chemical make up. After adding nutrient and mixing it into the aquarium, check the pH using whatever means you have. Whenever possible, rainwater or RO water is used mixed 50/50 with purified tap water to reduce its hardness. This greatly reduces the amount of CO2 we need to inject to manage pH. Never use a phosphate based pH down chemical to adjust your pH. Always remember, using any chemical to being your pH down will ruin your ability to accurately use our pH/kH/CO2 chart to determine CO2 concentration.
The pH of the water column will have a tendency to go up as the plants use the nutrients and produce oxygen. As a result, the pH needs to be checked periodically (and adjusted if necessary). This is particularly true if you are using a DIY yeast CO2 injection setup because you can't control the amount of CO2 being injected. To start out we suggest that you check pH on a daily basis. Each system will change pH at a different rate depending on a variety of factors. The type of growing substrate used, the size of the aquarium, kind of plants and even the age of the plants all effect the pH variations. That is the reason we recommend getting a serious CO2 system and eventually, a pH/CO2 controller.
~ Dwight.
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