Η απάντηση στο ερώτημα σου είναι στο site της seachem :
Q: Is it better to add Flourish Excel at night or in the morning based upon plant carbon uptake physiology?
A: Carbon intake is a function of photosynthesis. Based on this, it would be ideal to dose Flourish Excel during the day. But given that Flourish Excel can stay complexed as a carbon source for up to 24 hours before it dissipates, you can dose at any time of the day and the product will be available for the next 24 hours. Flourish Excel is not carbon dioxide and there is no impact on pH using Flourish Excel.
http://www.seachem.com/support/FAQs/FlourishExcel.html