The recommendation for fertilization with every watering is predicated on using a very dillute solution. The idea is to keep the concentration of Total Dissolved Solids (TDS) down in comparison to a more concentrated fertilizer solution so that the roots have an easier time. I'm sure someone will chime in with a more thorough explanation.

With regards to fertilizer, the numbers represent the number of pounds of say Nitrogen per 100 pounds of fertilizer. So yes, you are correct about 20 being more concentrated. It starts to get a little tricky with P and K as the numbers represent not just the P and the K but the oxides of them. Which IMO is a bit of a PITA. Here is the wikipedia explaining it.
NPK ratio

I look for low in nitrogen fertilizers. I fertilize my Epi after it blooms with a a half diluted fertilizer. The cactus I fertilize with a 1/4 dilution as often as I remember or if I feel like it. I do admit to being lazy and cheap at times. This is new behavior. I have been growing them hard with them just getting what they need from the soil, but most of my aloes were not blooming and some were large and gorgeous but I would like to see some bloom. I have not fertilized the cactus in the ground. My Epi is like your christmas cactus but different. Good luck.

There are several other teenagers here on the forum. Hobbies are a great form of education for Young and Old. It keeps us "ROOTED".

Thanks for all the help!!! Just a few more questions. After reading Microthrix's post, I wonder is fertilization really necessary? I know it helps for more rapid growth and encourages flowering, but can healthy plants be grown without fertilizer? Also, will putting the 16-12-12 slow release fertilizer I mentioned in the soil be helpful or hurtful? And finally, can slow release fertilizer pellets be dissolved in water to create liquid fertilizers?
Thanks again,
Matthew

Can succulents be grown without fertilizer? Yes. Can they be grown without nutrients? No, plants need nutrients. Sometimes the soil in which they are grown provides the needed nutrients. Sometimes the local water source provides the needed nutrients. It just depends. Some people grow in a container substrate that is almost completely inorganic and completely lacking in nutrients. In that case they need to supply nutrients with the water. If you look at some of the potting soil recipes around here you will see controlled release fertilizer as an option. Some people like to put a little in as a bit of a cushion in case they forget when watering. You cannot put controlled release fertilizer in water and create liquid fertilizer. That is why they are controlled release if they were water soluble the release would be instantaneous. The powders that make liquid fertilizer have to be completely water soluble.

Yes and no. It really matters on your soil. Some people do a pure grit mix and they need fertilizer. If you have a nutrient riche soil with native soil and some humus in it the plant can get all its nutrients for a couple of years from the soil. There is the concept of groqing plants "hard" versus growing them fat. I have always been for growing things hard. I grow most of my cactus outdoors in heat. sometimes this is not possible if one is a indoors grower with lights in the great north woods. Soils seem to play out after a couple of years. They need to be replaced. One can stretch this with fertilizer, but best to change the soil. I have gone for minimal ferilizing at the beginning of the year on the true cactus, periodic fertilizing for my arboreal tree cactus. I reward them when they bloom to set up the next blooming. Aloes, I am starting to fertilize lightly with every watering to see if I can get them to bloom. I think I will slow down in the heat of the summer(100 degrees) because they will be going dormant. I have a agave broomii that has not hardly grown at all and a huge aloe capitata that has not bloomed. There is a long list of non blooming aloes. So I am going to try something different. They are in fairly lean soil. They get absolutely gorgious aloe colors from sun and stress with my present fertilizing behavior but now I want blooms.

Thats what I thought nil13. Thanks for confirmation though!

A bit of cross posting...What he said. Different plants need different things.

Thanks to you as well wantonamara!

It probably matters too if they are in-ground versus in containers. My dad has a hedge of jade plants in-ground ... it is 5-6 feet tall. I am pretty sure (knowing my dad) that he does not fertilize these at all, and that hedge was planted over 20 years ago. In containers, I think eventually you may need some dilute fertilizer after a bit to make up for "old soil" that needs to be replenished with nutrients.