for the first question, I would think that not dosing the second week would eventually lead to too much of one nutrient and a deficiency of another -- an imbalance or nutrient limitation that would stunt the plants. Plus, I dont think that the amount left over at the end of the week is enough to last a whole other week, a day or two maybe.

second question - isn't that like the PPS fertilization method? trying to just dose exactly what the plants consume each day. That seems like it would be hard, and would require a large investment in time testing a bunch of parameters each day. Plus, there would still be a buildup of wastes like dissolved organic compounds that the plants aren't using and are just building up week after week.

you really can't get around doing waterchanges with a high-tech setup. In a non-co2 tank, frequent waterchanges will cause fluccuating co2 levels and induce algae. So very infrequent waterchanges work best in low light, no co2 tanks. They still need ferts, in non-limiting quantities, but they take a lot longer to use them up -- the need to dose is less frequent. Same dosages and nutrient levels, just less often -- I think -- I dont do a non-co2 tank with EI. My lowtech tank just sits there and I top off the water once every 3 months or so, and I dont dose it. So I dont know too much about the lowtech approach, but I have a great, successful, hightech, high light, co2-injected, EI tank with no algae and great plant growth

3rd question - yes it is like the guesstimative index in that the levels aren't written in stone. Taylor them to your specific tank's needs, lighting, type of plants, etc. But the whole point of EI is that no matter how you customize the doses for yourself, you are always dosing more than the plants can consume for every nutrient - which will eliminate the need to customize the dosing to account for a nutrient deficiency. That is where the suggested levels come into play. Tom has tested and found that in the best, perfect conditions with a lot of light and unlimiting co2 - these are the levels of nutrients that will be more than the plants can take in - levels that won't limit the plant in a nutrient - no matter how fast it's growing. These are the max. beneficial levels. You might use less in some situations, but you should never need more. (except maybe in very high light - I could be wrong though) The whole point is so that when your plants are doing bad, you know for sure that it's not a nutrient deficiency - and that you can look somewhere else for the cause - which will either be lighting or more likely co2. Good, consistent co2 is necessary for this to work however - or you will get algae. Not from excess nutrients, but from poor co2 not allowing the plants to grow, thus allowing the algae to use the nutrients...and grow.

I definately know that I'm NOT Tom, but I hope that'll get you started and answer some of the questions you have. He can fill in the blanks and correct me where I'm wrong.

Guh-Bye!
-Mike B-