Here is what most folks new to the hobby do not realize about plants and cycling and how to get this done. Plants eat ammonia in it NH4 (ammonium) form which is how most of the ammonia in water exists. The bacteria use the ammonia (NH3). Next, most aquatic plants actually host nitrifying bacteria.
So, the use of live plants in a tank will change the entire cycling paradigm. Given enough of the right sort of plants, one can avoid cycling, in the traditional sense completely. However, if you want to both plant and to cycle, it is best to do the planting first and any cycling after the plants have had some time to establish in a tank.
If you do a normal fishless cycle first and then you plant, what happens is about 1/2 to3/4 of the bacteria you worked to get established will not last. The plants will not leave enough ammonia for them. So you can cycle if you want, but then you will be wasting time and ammonia.
So here, in a nutshell, is what to do. Put in your substrate, if you want to add something into the bottom part of the substrtae to help the plants, that is fine. In days gone by we could get Laterite for this. No longer. But there are other similar things one can add a bit of into tthe bottom 1/3 of the substrate. Some of Seachem Flourite will work, it is sold as a stand alone substrate but I do not like it for this. So if you are going to use it as I suggest, get the smallest amount you can unless you are doing a larger tank.
When you are adding the substrate to the tank add about 1 inch and then sprinkle in some of the flourite. Mix up the substrate and flouroite and then add the balance of your substrate. You can use small gravel or sand either will work OK. If you are keeping corys they prefer sand but a small sized, non-sharp gravel will work also.
Then plant the tank. I would suggest you go to the Tropica site for advice on this front:
https://tropica.com/en/
You cannot read too much there.
Most plants in the hobby are grown for the hobby and when you buy them they are loaded nutritionally. So they should do fine initially without any added fertilizers. What they need to do is to establish themselves in the tank. In the substrate this means rooting. Give the tank about two weeks for this. Then you can think about fertiliing. Bear in mund if you are going to do some cyccling you will be adding ammonia. So the plants should only need trace and micronutrients for the most part if at all,
Now is it time for fish. You have two choices. One is to stock slowly and let the plants and the limited amount of bacyteria they brought in do the work. As you add fish the bacteria and/or plant mass will increase. You will need to test for ammonia during this stocking ti insure ammonia is being handled and no nitrite is involved either.
The next option you have is one which will allow you to stock fully all at once. The key to doing this is to know how much ammonia the tank can handle at the end of the establish-the-plants period. The best way to do this is to add a known amount of ammonia and see how long it takes to be cleared. However, some plants are more sensitive than other to ammonia.
So what you should do is as follows. Add ammonia to produce 1 ppm in the tank. Then test in 12 hours. If it is 0 ppm, you know you are along the way to being well cycled. If you get a reading at 12 hours, then wait another 12 and retest. If you still get an ammonia reading then you need to do more to "cycle" the tank. However, if you get that 0 ppm at either 12 or 24 hours, you have two options.
If you want to do a full stocking, then repeat the test but with 2 ppm of ammonia. However, the ability to clear 1 ppm in 24 hours or less means you can start to stock gradually. Do a water changes and consider about 1/3 stocking and go from there as long as ammonia and nitrite are at 0. If you want to stock all in one go, then proceed as below.
Do the same 12 and 24 hour tests after adding 2 ppm of ammonia. If you get 0 at either one, you can then do a big water change and begin stocking the tank with as many fish as would constitute a full load. You can still stock in a couple of goes, but you should do the bulk of stocking right away. Once you begin adding fish you cannot add ammonia any more.
Your cycle will be handled by a combination of plants and bacteria. The more plants you have and the faster growing they are, the more ammonia they will handle and the less bacteria you will have. However, no matter how many plants you have, there will still always be some number of bacteria colonizing.
The best part about having live plants is that when they consume ammonia, they do not create any nitrite or nitrate. In fact they may consume any nitrate the bacteria make.
The above is a basic guide to this planting/cycling process. Because there are such a variety of plant of which some gobble ammonia but other uses it slowly, and because the mass of plants in a tank can vary based on the owners needs and desires, it is extremely difficult to reduce it to the same formulaic level one can in traditional cycling. There ammonia makes nitrite and then nitrate. We know how much of this to expect and can test it all. And those results let us know where in the cycle things stand. It is less precise when plants are involved because of how much variability is possible.
I do not know of any way for those new to planted tanks to assess the ability of a planted tank to handle the cycling chore except by using a dose and test methodolgy as I laid out above. Those of us who have been planting and cycling for some number of years often develop aa "sixth sense" in this regard. We have learned which plants and how many to use and then how many fish we can add at any stage. This knowledge comes from experience.
