First off, welcome to the forum! We're glad to help you here any time!
I have a marimo moss ball in my 5.5 gallon medium tech planted tank where I run a high light, inject Co2
and I dose API Co2
Booster every now and then (when I remember
I really haven't seen that much growth out of it. They take forever to grow, so I'm not surprised. Likewise, in my 16 low tech tank, I have 2 that haven't grown at all since I got them. These guys are 10 years+ old.
I personally wouldn't bother spending the money on the API, you won't see any immediate growth out of them any way. Many people just leave them be and they still grow and reach decent sizes. If you're still a member here in 15 years, feel free to post how it turnout for you!
I'm going to let the real plant experts help you out with the real specific stuff now, good luck!
My tanks (so far
5.5 gallon Planted Dwarf Puffer tank (2 Dwarf Puffers and a lot of RCS!)
16 Gallon Planted
(GBR pair, 3 amano shrimp and a whole bunch of snails!)