I think it might be this one, I can't find the original link though. There are some that are a little cheaper, but they don't seem to have that little window on the side. https://smile.amazon.com/dp/B082FJ37D1/ref=cm_sw_r_cp_apa_glt_fabc_WTBB16VWSQ9T84NMH6TY
Slow releasing nitrogen fertilizer, it dissolves every time you water it so it doesn't kill your tree by over fertilizing and it continues to feed the tree.
Here where I get mine:) https://www.amazon.com/dp/B001CZ9R1A/ref=cm_sw_r_cp_apa_glt_fabc_1BBKVY4A4VA25NXK436Q?_encoding=UTF8&psc=1
I see you've also got those AC infinity fans.
A little tip, if you unscrew the rubber feet, the small end of these hooks fits perfectly in the hole and makes the fans readily hangable.