There are no simple rules for use with planted tanks. There are a number of potential variables involved in terms of knowing if any given planted tanks needs ferts and then what kind. What there is are basic rules for plants.
In a planted tank there are 3 major variables involved- light. CO@ and ferts. For any given tank these 3 things need to be in balance. Too much or too little of any of these things and you may have problems with algae or with undernourished plants.
How much of what is needed depends on what amount of plants one had, what specific plants one has, what nutrients might be in one's source water, how many and what types of fish one has and then what size tank.
Trouble with deep substrate is more myth than fact. I ran my high tech planted tank with pressurized CO2 added I had 3 inches of small gravel. It ran for almost 10 years and i never had any gas related issues in the substrate. I have had planted tanks which needed minimal care and some which needed more care and then the high tech tank.
To be successful with plants shares one thing with having successful stocking. We need to learn about both to succeed. I was lucky when I began adding live plants to tanks in that I had gardened outdoors for many years before I even had my first tank. Mos of he principles involved are the same for both land and aquatic plants.
I think the best advice I can offer is to send you to the Tropica site. Tropica has been one of the world's leading supplier of plant for many decades. Some of the plants you will see in many tanks were either discovered by Tropica and its founder Holgar Wendelov:
Mr. Holger Windeløv, founder of Tropica Aquarium Plants, started as a fish tank hobbyist who became increasingly interested in growing aquatic plants for his own use and for fellow hobbyists.
He then started to develop greenhouse facilities and sell the plants he produced, creating the company named Tropica Aquarium Plants in 1970.
Every year since then, Holger Windeløv has been travelling to explore for new plants - sometimes to exotic locations such as chalky, crystal-clear springs in South America, or murky, muddy ponds in Southeast Asia, and sometimes to extensive collections of aquatic plants, nurseries, and meetings with aquarists throughout the world.
In 2004, the company was sold to JPS Clemens, due to a generational change and the new owners established a new nursery garden in 2007 as the base of a long-term strategy.
Tropica Aquarium Plants aims to increase the joy and experience of having an aquarium as a hobby. The company develops, produces and sells aquarium plants, fertiliser and aquarium equipment.
I suggest you head over to the Tropica site and read read read:
http://tropica.com/en/
I have only used Tropica liquid fertilizers now for 24 years. At my peak I had 13 planted tanks. However, old age is forcing me to cut way back. I am down to only 11 tanks in all but 3 of them are not planted. In addition to doing planted community tanks I used to have more pleco breeding and grow tanks than planted communities. Today I am almost done with any form of breeding and am down to just 2 tanks for this.
What you will find as there are a lot of differing opinions on all of this. The trick for each of us is to learn what works for our tanks and then the plants will thrive. Be prepared for some trial and error and some failure. There is nothing wrong with failing as long as we learn from out mistakes and do not repeat them.
Finally, getting good with plants tajes effort and especially learning. I tell folks new to live plants that they should start with the easier to manage plants and then move up the learning curve. It is like learning to drive. We do not start out by trying to drive an Indy 500 race car.
p.s. All plants need food and they basically use chemicals. When theses are not naturally available for us in our tanks, we add ferts. I have made a few mistakes over the years that killed fish. However, adding ferts for the plants was not one of the causes.
