Substrate is like the plates and bowls on your table. It can hold nutrients for the plants just like plates and bowls hold food. But you need to add the fertilizer, just like you put food on the plates.
Some substrates are composed of elements that are plant nutrients, but the substrate is so dense it does not dissolve in the water, so those elements are not really plant nutrients. Just like the plates and bowls do not help you with your vitamins and minerals, even if they are made of those minerals. The elements that make up the granules of EC never become available to the plants.
Some substrates do come pre-loaded with some fertilizer. I would not buy a substrate just because it has some fertilizer in it.
Buy a substrate with a high cationic exchange capacity. This is the way a substrate holds certain elements available for the plants. When you add fertilizers they are kept in reserve in the substrate.
Thanks, Diana. Interesting analogy! So, to answer my own question from that... If I don't do dirt, I will do fert. (Hey, that rhymed!)
EC has high CEC so it's a good choice. Although it has some nutrients, it does not have all of the minerals to completely sustain plant life for any given time. It does however have the capacity to store nutrients.
I guess with all the different fertilizers out there, I just don't know which ones I really will need. If I have to use flourish and tabs at a minimum, does the high CEC mean it serves as a buffer or does it store the nutrients instead of letting them float around in the water?
In addition to flourish, do I also need to dose trace, potassium, iron, etc? I guess what would be ideal would be to have one bottle of whatever to dose periodically, kind of a one a day vitamin. I'm finding I'm quite horrible at figuring out what kind of algae or mineral deficiency exists in my smaller tank. I've found cheat sheets and similar, but it seems whenever something goes wrong, I can't find exactly what I'm looking at in my tank. It's one of those, you need to know what your looking for before you can find it.
I know it gets easier with practice, so I think I will go with the last few months of researching this and go for it. Heh, plastic plants were so much easier