03-14-2010, 03:14 PM
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You have algae problems because the light is too intense to balance the nutrients for what the plants can use, in a nutshell.
Now to specifics. Reducing the light intensity will help a lot, so that is the first step which you've already decided.
There is also a problem with your additives; you do not need Excel, what it is doing is throwing the nutrients/light out of balance even more. Plus, when you use it sporadically it harms the plants. Excel is a carbon supplement, and plants need a steady supply of carbon every day or they cannot photosynthesize. As Tom Barr has expertly pointed out elsewhere, variations in CO2/carbon impedes the plant's ability to photosynthesize. Just as you can grow healthy plants without CO2 diffusion, so you can do it without Excel which is the same basic thing, carbon, only in a different form. Stop adding Excel and it will also help the algae problem.
As for the other nutrients, in Flourish, once a week should be sufficient to balance your light (when it is reduced) and fish load (nitrogen and CO2 come from the fish and biological processes). But dose it the day after a water change; chances are you are using a water conditioner that detoxifies heavy metals, and some heavy metals are required plant micro-nutrients: iron, copper, zinc, manganese and nickel. I contacted Seachem on this, and was advised that Prime (and other conditioners that detoxify metals) would make the nutrients in Flourish ineffective. But using Flourish 24 hours later is fine, since Prime only detoxifies for about 24 hours.
Follow this and your balance will be established between light and nutrients, and algae will not be a problem.