The issue is always balance, which is what most posts are dealing with in various ways. You can have a thriving, lush 90g planted tank dosing 1 teaspoon of Flourish a week. Or you can have a thriving, lush planted 90g tank dosing dry ferts every day. But doing the second method in a tank balanced for the first method will be disaster.
First thing one has to decide is what you want in the end, as a planted tank. Then you work out the balance to achieve that end, which includes the light intensity [duration can always be adjusted, but if the intensity is not sufficient for what you want, or is too high for what you want, trouble will follow], fish stocking, fish feedings, and nutrient supplementation. The nutrient supplementation includes all nutrients you intend to add artificially, meaning, not relying on what is there naturally. And the latter depends upon the fish and feeding, plus your maintenance.
Tom Barr once told me that you first select your light--keeping in mind that you need the light suitable for the type of planted tank--then you add nutrients until you work out the balance. Another source, can't remember who it was, but more than one has said this, wrote that you can use the plants' response to tell you if more or less is needed. This is a bit tricky, admittedly, until one becomes experienced.
Someone mentioned the minimal macros in Flourish Comprehensive. This product is not intended as a full-source nutrient provider. As the name suggests, it is intended to "supplement" nutrients in a planted tank with fish. It assumes some nutrients will already be available. Hard mineral nutrients (calcium, magnesium, potassium) are minimal because these will be present in most municipal water supplies; however, for those who like me and any living in the Pacific NW of the USA or SW BC, we have very soft water and the hard minerals in Flourish Comp are no where near sufficient, so we have to add them. Concerning other nutrients, the only ones not included are oxygen, hydrogen and carbon, all of which occur naturally in the aquarium. And from all this, one can see that Flourish is also intended for natural or low-tech setups.
The amount of Flourish Comp you need to add will depend upon the light, and the tank's biology. Over 4 years now, I have experimented a bit. I am currently dosing Flourish Comp once a week in all tanks, and Flourish Trace once a week. Flourish Comp twice a week worked in all but one tank (algae increased in this tank with twice weekly doses) but since I have been substituting Trace for the second dose, the plants seem better and I am not seeing algae. I do not add any form of carbon, so I have to balance anything I do, including light duration, with the natural CO2.
Last edited by Byron; 04-20-2013 at 02:32 PM..