Semi-Hydro seemed to be more popular a few years ago and I cannot recall seeing many recent posts. Maybe put Semi Hydro in the search box and read some of the old threads.

Here is a link to very long past thread about fertilizer (And Urea) that contains valuable information.

Long past discussion

I think the 20-10-20 Grow More without the UREA should be fine.....it is just that marketing people will tell you all sorts of things to make a sale.

I am sure your 20-10-20 fertilizer will be fine. I grow a few things in semi hydroponic and have switched fertilizers a few times without noticing much of a difference. I have never used a completely balanced fertilizer.

You may want to checkout this page and some of the other articles on the site.

http://firstrays.com/free-information/feeding-and-watering/measurement-handling-application-of-fertilizers/nitrogen-management-calculator/