Bonsai is a manicure style or beter to say tradition. It can be done with about any tree.. Some are more popular because of the grow characteristics and easier to get that distinct bonsai look.. It the shape and style making it a bonsai not the sp.
https://www.bonsainut.com/threads/best-fertilizer-for-chinese-elm.7135/
Fertilizing any plant in pot is always a tricky thing to give a strict conclusive answer to..
In general the most important part of the fertilizer is the NPK (Macro) contents. These are always labled in numbers for example 15-15-15 or 7-14-28. This tells you the amount of N-P-K.. Depending on sp. you want to grow some need a lot N others hate it.. Flowering plants need a higher PK contents than non flowering plants. Flowering plants like a lot of N in their vegitative periode when they need to grow mass, the period they are flowring N should be reduced P-K should be upped to get beter results.
There are many different combinations of NPK contents around, all depending on what you like to grow.. 15-15-15 for example is ideal for lush grass lands.. 7-14-28 is ideal for flowring plants during their flowering periode.
Than there are artificial fast release fertilizers and biological slow release fertilizers.
The fast release fertilizers are the salts disolved in water..The pro is it is readily available to the plant for quick results. The con is, it contains lots of salts, putting a lot of this in the soil will in the end cause a salt accumulation making the soil salty and useless.. No problem for fruiting annual plants only living one season, you start over each year with a fresh setup.. If you would give this a lot to a perrenial plant standing several years on the same soil/pot. Than you would need to replace this soil when it becomes over saturated with salts. So for perinnials like a tree in a container it is beter to use an organic slow release fert instead to keep the soil long term healthy.
It is a lot, to take in.. That's what makes the house plant nurseries flourish and survive.. People do not take it in, they put in what ever is provided and what ever the manual says.. Mainly easy fast release ferts once a month all summer long.. Making the plant do good for a periode and than likely will die off if the soils isn't replaced. And than you buy a new one.. Circle is round again. But if you like you and with the proper care you can have the same house plant for many years if not decades in the same pot.. I have a few which are over 15 years old and still in the same soil.
And actualy not getting ferts that often. Maybe twice in the summer, as long as they look healthy it's ok.
This is a bit in a nutshell, there is much more, many books are written about it.. About impossible to put it in a nutshell, even a bag of nuts wouldn't be enough..